Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 88315 

• Are not significant regulatory 

actions subject to review by the Office 

of Management and Budget under 

Executive Orders 12866 (58 FR 51735, 

October 4, 1993) and 13563 (88 FR 

21879, April 11, 2023); 

• Do not impose an information 

collection burden under the provisions 

of the Paperwork Reduction Act (44 

U.S.C. 3501 et seq.); 

• Are certified as not having a 

significant economic impact on a 

substantial number of small entities 

under the Regulatory Flexibility Act (5 

U.S.C. 601 et seq.); 

• Do not contain any unfunded 

mandate or significantly or uniquely 

affect small governments, as described 

in the Unfunded Mandates Reform Act 

of 1995 (Pub. L. 104–4); 

• Do not have federalism implications 

as specified in Executive Order 13132 

(64 FR 43255, August 10, 1999); 

• Are not subject to Executive Order 

13045 (62 FR 19885, April 23, 1997) 

because they approve a state program; 

• Are not significant regulatory 

actions subject to Executive Order 

13211 (66 FR 28355, May 22, 2001); and 

• Are not subject to requirements of 

section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (15 U.S.C. 272 note) because 

application of those requirements would 

be inconsistent with the CAA. 

In addition, the SIP is not approved 

to apply on any Indian reservation land 

or in any other area where EPA or an 

Indian tribe has demonstrated that a 

tribe has jurisdiction. In those areas of 

Indian country, the proposed rule does 

not have tribal implications and will not 

impose substantial direct costs on tribal 

governments or preempt tribal law as 

specified by Executive Order 13175 (65 

FR 67249, November 9, 2000). 

Executive Order 12898 (Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations, 59 FR 7629, 

Feb. 16, 1994) directs Federal agencies 

to identify and address 

‘‘disproportionately high and adverse 

human health or environmental effects’’ 

of their actions on minority populations 

and low-income populations to the 

greatest extent practicable and 

permitted by law. EPA defines 

environmental justice (EJ) as ‘‘the fair 

treatment and meaningful involvement 

of all people regardless of race, color, 

national origin, or income with respect 

to the development, implementation, 

and enforcement of environmental laws, 

regulations, and policies.’’ EPA further 

defines the term fair treatment to mean 

that ‘‘no group of people should bear a 

disproportionate burden of 

environmental harms and risks, 

including those resulting from the 

negative environmental consequences of 

industrial, governmental, and 

commercial operations or programs and 

policies.’’ 

EPD did not evaluate EJ 

considerations as part of its SIP 

submittals; the CAA and applicable 

implementing regulations neither 

prohibit nor require such an evaluation. 

EPA did not perform an EJ analysis and 

did not consider EJ in these proposed 

actions. Due to the nature of the actions 

being proposed here, these proposed 

actions are expected to have a neutral to 

positive impact on the air quality of the 

affected area. Consideration of EJ is not 

required as part of these proposed 

actions, and there is no information in 

the record inconsistent with the stated 

goal of E.O. 12898 of achieving EJ for 

people of color, low-income 

populations, and Indigenous peoples. 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Carbon monoxide, 

Incorporation by reference, Nitrogen 

dioxide, Ozone, Particulate matter, 

Reporting and recordkeeping 

requirements, Sulfur oxides, Volatile 

organic compounds. 

Authority: 42 U.S.C. 7401 et seq. 

Dated: December 14, 2023. 

Jeaneanne Gettle, 

Acting Regional Administrator, Region 4. 

[FR Doc. 2023–28105 Filed 12–20–23; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 131 

[EPA–HQ–OW–2023–0222; FRL 10760–01– 

OW] 

RIN 2040–AG30 

Water Quality Standards To Protect 

Aquatic Life in the Delaware River 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: On December 1, 2022, the 

U.S. Environmental Protection Agency 

(EPA) determined that revised water 

quality standards are necessary to 

protect aquatic life in certain water 

quality management zones of the 

Delaware River. Specifically, the EPA 

issued an Administrator’s 

Determination, pursuant to the Clean 

Water Act (CWA), finding that a revised 

designated use to protect aquatic life 

propagation and corresponding 

dissolved oxygen criteria to protect that 

use are necessary in Zone 3, Zone 4, and 

the upper portion of Zone 5 (in total, 

river miles 108.4 to 70.0) of the 

Delaware River. The CWA requires the 

EPA to publish proposed water quality 

standards following an Administrator’s 

Determination. Thus, the EPA is 

proposing to promulgate an aquatic life 

designated use that includes 

propagation and protective water 

quality criteria for dissolved oxygen for 

Zone 3, Zone 4, and upper Zone 5 of the 

Delaware River. 

DATES: Comments must be received on 

or before February 20, 2024. Public 

hearing: the EPA will hold two public 

hearings during the public comment 

period. Please refer to the 

SUPPLEMENTARY INFORMATION section for 

additional information on the public 

hearings. 

ADDRESSES: You may send comments, 

identified by Docket ID No. EPA–HQ– 

OW–2023–0222, by any of the following 

methods: 

• Federal eRulemaking Portal: 

https://www.regulations.gov/ (our 

preferred method). Follow the online 

instructions for submitting comments. 

• Mail: U.S. Environmental 

Protection Agency, EPA Docket Center, 

Office of Water Docket, Mail Code 

28221T, 1200 Pennsylvania Avenue 

NW, Washington, DC 20460. 

• Hand Delivery or Courier: EPA 

Docket Center, WJC West Building, 

Room 3334, 1301 Constitution Avenue 

NW, Washington, DC 20004. The Docket 

Center’s hours of operations are 8:30 

a.m.–4:30 p.m., Monday through Friday 

(except Federal holidays). 

Instructions: All submissions received 

must include the Docket ID No. for this 

rulemaking. Comments received may be 

posted without change to https://

www.regulations.gov/, including any 

personal information provided. For 

detailed instructions on sending 

comments and additional information 

on the rulemaking process, see the 

‘‘Public Participation’’ heading of the 

SUPPLEMENTARY INFORMATION section of 

this document. 

FOR FURTHER INFORMATION CONTACT: 

Hannah Lesch, Office of Water, 

Standards and Health Protection 

Division (4305T), Environmental 

Protection Agency, 1200 Pennsylvania 

Avenue NW, Washington, DC 20460; 

telephone number: (202) 566–1224; 

email address: Lesch.Hannah@epa.gov. 

SUPPLEMENTARY INFORMATION: This 

proposed rule preamble is organized as 

follows: 

I. Public Participation 

A. Written Comments 

B. Participation in Public Hearings 

II. General Information 


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88316 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

1Before any water quality-based effluent limit 

would be included in an NPDES permit, the 

permitting authority (here, the states of Delaware, 

New Jersey, and Pennsylvania), must first 

determine whether a discharge ‘‘will cause or has 

the reasonable potential to cause, or contribute to 

an excursion above any WQS.’’ 40 CFR 

122.44(d)(1)(i) and (ii). 

A. Does this action apply to me? 

III. Background 

A. Statutory and Regulatory Authority 

B. Relevant Ecological History of the 

Delaware River 

C. Administration of Water Quality 

Standards in the Delaware River 

D. Currently Applicable Aquatic Life 

Designated Uses and Dissolved Oxygen 

Criteria 

E. Summary of the EPA’s Administrator’s 

Determination 

IV. Proposed Water Quality Standards 

A. Scope of EPA’s Proposed Rule 

B. Proposed Aquatic Life Designated Use 

C. Dissolved Oxygen Criteria To Protect 

Aquatic Life Propagation 

V. Endangered Species Act Consultation 

VI. Applicability 

VII. Conditions Where Federal Water Quality 

Standards Would Not Be Promulgated or 

Would Be Withdrawn 

A. Conditions Where Federal Standards 

Would Not Be Promulgated 

B. Conditions Where Federal Standards 

Would Be Withdrawn 

VIII. Alternative Regulatory Approaches and 

Implementation Mechanisms 

A. Water Quality Standards Variances 

B. NPDES Permit Compliance Schedules 

C. Clean Water Act Section 303(d)/305(b) 

Water Quality Assessments 

IX. Economic Analysis 

X. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 14094: Modernizing Regulatory 

Review 

B. Paperwork Reduction Act (PRA) 

C. Regulatory Flexibility Act (RFA) 

D. Unfunded Mandates Reform Act 

(UMRA) 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

I. National Technology Transfer and 

Advancement Act (NTTAA) 

J. Executive Order 12898: Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations and Executive Order 14096: 

Revitalizing Our Nation’s Commitment 

to Environmental Justice for All 

I. Public Participation 

A. Written Comments 

Submit your comments, identified by 

Docket ID No. EPA–HQ–OW–2023– 

0222, at https://www.regulations.gov 

(the EPA’s preferred method), or the 

other methods identified in the 

ADDRESSES section. Once submitted, 

comments cannot be edited or removed 

from the docket. The EPA may publish 

any comment received to its public 

docket. Do not submit to the EPA’s 

docket at https://www.regulations.gov 

any information you consider to be 

Confidential Business Information (CBI), 

Proprietary Business Information (PBI), 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). Please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets for additional 

submission methods; the full EPA 

public comment policy; information 

about CBI, PBI, or multimedia 

submissions; and general guidance on 

making effective comments. 

B. Participation in Public Hearings 

The EPA is offering two public 

hearings so that interested parties may 

also provide oral comments on this 

proposed rulemaking. For more details 

on the public hearings and to register to 

attend the hearings, please visit https:// 

www.epa.gov/wqs-tech/water-qualitystandards-delaware-river. 

II. General Information 

A. Does this action apply to me? 

A range of individuals and entities 

could be affected by this rulemaking, if 

finalized. For example, entities that 

discharge pollutants to certain waters 

under the jurisdiction of the states of 

Delaware, New Jersey, and 

Pennsylvania—such as industrial 

facilities and municipalities that 

manage stormwater, separate sanitary, 

or combined sewer systems—could be 

indirectly affected by this rulemaking 

because Federal water quality standards 

(WQS) promulgated by the EPA would 

be the applicable WQS for these waters 

for CWA purposes (Table 1 of this 

preamble). Specifically, these WQS 

would be the applicable standards that 

must be used in CWA regulatory 

programs, such as permitting under the 

National Pollutant Discharge 

Elimination System (NPDES) under 

CWA section 402 1 and identifying 

impaired waters under CWA section 

303(d). In addition, individuals and 

entities who rely on or benefit from 

aquatic life in those waters may be 

indirectly affected. 

TABLE 1—ENTITIES POTENTIALLY AFFECTED BY THIS PROPOSED RULE

Category Examples of potentially affected entities 

Industry ................................................................ Industrial point sources discharging to certain waters in Delaware, New Jersey, and Pennsylvania. Commercial fishing operations that harvest fish. 

Municipalities, including those with stormwater 

or combined sewer system outfalls.

Publicly owned treatment works or similar facilities responsible for managing stormwater, separate sanitary, or combined sewer systems that discharge to certain waters in Delaware, 

New Jersey, and Pennsylvania. 

Recreation and Tourism ...................................... Anglers and tourists seeking recreational opportunities related to aquatic life in certain waters 

in Delaware, New Jersey, and Pennsylvania. 

This table is not intended to be 

exhaustive, but rather provides a guide 

for readers regarding entities that could 

be indirectly affected by this action. If 

you have questions regarding the 

applicability of this action to a 

particular entity, consult the person 

listed in the FOR FURTHER INFORMATION

CONTACT section above. 

III. Background 

A. Statutory and Regulatory Authority 

CWA section 101(a)(2) establishes a 

national goal of ‘‘water quality which 

provides for the protection and 

propagation of fish, shellfish, and 

wildlife, and provides for recreation in 

and on the water’’ (hereafter, 

collectively referred to as ‘‘101(a)(2) 

uses’’ or ‘‘101(a)(2) goals’’), wherever 

attainable. The EPA’s regulation at 40 

CFR 131.10(g) implements this statutory 


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Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 88317 

2Hardy, C.A. (1999). Fish or Foul: A History of 

the Delaware River Basin Through the Perspective 

of the American Shad, 1682 to the Present. 

Pennsylvania History, 66(4), 506–534. https://

digitalcommons.wcupa.edu/hist_facpub/13; Secor, 

D.H. and Waldman, J. (1999). Historical abundance 

of Delaware Bay Atlantic sturgeon and potential 

rate of recovery. American Fisheries Society 

Symposium. 23. 203–216. https://

www.researchgate.net/publication/291783957_

Historical_abundance_of_Delaware_Bay_Atlantic_

sturgeon_and_potential_rate_of_recovery; Smith, 

T.I.J., & Clugston, J.P. (1997) Status and 

management of Atlantic sturgeon, Acipenser 

oxyrinchus, in North America. Environmental 

Biology of Fishes 48, 335–346. https://doi.org/ 

10.1023/A:1007307507468; National Marine 

Fisheries Service. (1998). Recovery Plan for the 

Shortnose Sturgeon (Acipenser brevirostrum). 

Prepared by the Shortnose Sturgeon Recovery Team 

for the National Marine Fisheries Service, Silver 

Spring, Maryland. 104 pages. https://repository.

library.noaa.gov/view/noaa/15971. 

3Stoklosa, A.M., Keller, D.H., Marano, R., and 

Horwitz, R.J. (2018). ‘‘A Review of Dissolved 

Oxygen Requirements for Key Sensitive Species in 

the Delaware Estuary.’’ Academy of Natural 

Sciences of Drexel University. November 2018. 

https://www.nj.gov/drbc/library/documents/

Review_DOreq_KeySensSpecies_DelEstuary_

ANStoDRBCnov2018.pdf. 

4See citations in footnote 2 of this preamble; 

Atlantic States Marine Fisheries Commission. 

(1981). Interstate Fisheries Management Plan for the 

Striped Bass. http://www.asmfc.org/uploads/file/ 

1981FMP.pdf. 

5United States Environmental Protection Agency. 

(2021). Factsheet on Water Quality Parameters: 

Dissolved Oxygen. July 2021. Document ID: EPA 

841F21007B. https://www.epa.gov/system/files/ 

documents/2021-07/parameter-factsheet_do.pdf; 

United States Environmental Protection Agency. 

(2023a). Indicators: Dissolved Oxygen. June 9, 2023. 

https://www.epa.gov/national-aquatic-resourcesurveys/indicators-dissolved-oxygen. 

6Hardy (1999); Delaware River Basin 

Commission. (2022a). Analysis of Attainability: 

Improving Dissolved Oxygen and Aquatic Life Uses 

in the Delaware River Estuary. September 2022 

Draft. See section 3—‘‘Factors that can Improve 

Dissolved Oxygen in the Fish Maintenance Area.’’ 

https://www.nj.gov/drbc/library/documents/

AnalysisAttainability/AnalysisAttainability_

DRAFTsept2022.pdf. 

7 Delaware River Basin Commission. (2022b). 

Modeling Eutrophication Processes in the Delaware 

River Estuary—Three-Dimensional Water Quality 

Model. https://www.nj.gov/drbc/library/documents/ 

AnalysisAttainability/WQModelCalibrationRpt_

DRAFTsept2022.pdf. 

8Miskewitz, R. and Uchrin, C. (2013). In-Stream 

Dissolved Oxygen Impacts and Sediment Oxygen 

Demand Resulting from Combined Sewer Overflow 

Discharges. Journal of Environmental Engineering, 

139(10). https://doi.org/10.1061/(ASCE)EE.1943- 

7870.0000739. 

provision by requiring that WQS protect 

101(a)(2) uses unless those uses are 

shown to be unattainable. 

Under the CWA, states have the 

primary responsibility for reviewing, 

establishing, and revising WQS 

applicable to their waters (CWA section 

303(c)). WQS define the desired 

condition of a water body, in part, by 

designating the use or uses to be made 

of the water and by setting the numeric 

or narrative water quality criteria to 

protect those uses (40 CFR 131.2, 

131.10, and 131.11). There are two 

primary categories of water quality 

criteria: human health criteria and 

aquatic life criteria. Human health 

criteria protect designated uses such as 

public water supply, recreation, and fish 

and shellfish consumption. Aquatic life 

criteria protect designated uses such as 

protection and propagation of fish, 

invertebrates, and other aquatic species. 

Regardless of their category, water 

quality criteria ‘‘must be based on sound 

scientific rationale and must contain 

sufficient parameters or constituents to 

protect the designated use. For waters 

with multiple use designations, the 

criteria shall support the most sensitive 

use’’ (40 CFR 131.11(a)(1)). 

States are required to hold a public 

hearing to review applicable WQS at 

least once every three years and, if 

appropriate, revise or adopt new 

standards (CWA section 303(c)(1); 40 

CFR 131.20(a)). Every three years, states 

must also reexamine water body 

segments that do not include the 

101(a)(2) uses to determine if new 

information has become available that 

indicates the 101(a)(2) uses are 

attainable, and if so, revise the WQS 

accordingly (40 CFR 131.20(a)). Any 

new or revised WQS must be submitted 

to the EPA for review and approval or 

disapproval (CWA section 303(c)(2)(A) 

and (c)(3)). 

CWA section 303(c)(4)(B) 

independently authorizes the 

Administrator to determine that a new 

or revised standard is necessary to meet 

CWA requirements; this action is 

frequently referred to as an 

‘‘Administrator’s Determination.’’ 

Pursuant to CWA section 303(c)(4)(B), 

after making an Administrator’s 

Determination, the EPA must propose 

and promulgate WQS specified in the 

Administrator’s Determination. If a state 

adopts and the EPA approves WQS that 

address the Administrator’s 

Determination prior to the EPA’s 

promulgation, then the EPA would no 

longer be required to promulgate WQS. 

B. Relevant Ecological History of the 

Delaware River 

The Delaware River has historically 

been home to numerous species of 

ecological, recreational, and economic 

importance; however, centuries of 

anthropogenic water quality impacts 

and habitat degradation, peaking in the 

mid-twentieth century, made portions of 

the river unsuitable for many aquatic 

species. In the 1700s and 1800s, many 

native fish species in the Delaware River 

faced declining populations due to 

overharvesting and the installation of 

physical barriers that prevented fish 

passage.2 Further population declines of 

native oxygen-sensitive species—such 

as the Atlantic Sturgeon (Acipenser 

oxyrinchus oxyrinchus), American Shad 

(Alosa sapidissima), Shortnose Sturgeon 

(Acipenser brevirostrum), and Striped 

Bass (Morone saxatilis), among 

others 3—were linked to accelerating 

degradation of water quality through the 

first half of the 1900s, including 

seasonal anoxia (i.e., absence of oxygen) 

by the mid-twentieth century in Zone 3, 

Zone 4, and the upper portion of Zone 

5 of the Delaware River.4

Dissolved oxygen is an important 

water quality parameter that can 

significantly influence the distribution 

and abundance of aquatic organisms 

and ecological relationships in aquatic 

ecosystems. Aquatic organisms need to 

obtain adequate levels of dissolved 

oxygen to maintain and support normal 

functioning, including during sensitive 

life stages, such as spawning, larval 

development, and juvenile growth.5 As 

dissolved oxygen levels decrease in a 

waterbody, the rate at which aquatic 

organisms can obtain oxygen from the 

water decreases, resulting in impaired 

growth and reduced survival. 

Maintaining a healthy ecosystem 

requires dissolved oxygen levels above 

thresholds that impair growth and 

survival of aquatic species. 

1. Causes of Low Dissolved Oxygen in 

the Specified Zones of the Delaware 

River 

Discharges of untreated or poorly 

treated municipal and industrial 

wastewater into the specified zones of 

the Delaware River have historically 

been a major cause of water quality 

degradation, including oxygen 

depletion.6 While conditions have 

significantly improved, inputs of 

oxygen-consuming wastes from 

wastewater dischargers, especially 

ammonia (NH3) and ammonium (NH4

+) 

(which in combination are hereafter 

referred to as ‘‘ammonia nitrogen’’), as 

well as sediment-water ammonium flux 

and sediment oxygen demand continue 

to be significant sources of oxygen 

demand in the specified zones of the 

Delaware River.7

Along the Delaware River, untreated 

wastewater discharges typically occur 

during and after rainfall due to 

combined sewer overflows (CSOs), 

which are a source of nutrients (i.e., 

nitrogen and phosphorus), sediments, 

and toxic contaminants, and can lead to 

increased chemical and biological 

oxygen demand in the river.8 Although 

the cumulative impact of historical 


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88318 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

9Miskewitz and Uchrin (2013). 

10Hardy (1999). 

11Philadelphia Water Department. (2022). 

Combined Sewer Management Program Annual 

Report. Stormwater Management Program Annual 

Report. See Appendix D—‘‘NPDES Annual CSO 

Status Report FY 2022,’’ Table 2—‘‘Overflow 

Summary for 7/1/2021–6/30/2022.’’ https://water.

phila.gov/pool/files/fy22-npdes-annual-report.pdf. 

12United States Environmental Protection 

Agency. (2023b). Ammonia. https://www.epa.gov/ 

caddis-vol2/ammonia. 

13Each individual reporting period is one month 

long. For the reporting period ending on September 

30, 2022, Florence Township Municipal Building 

discharged an average of .07 mg/L of ammonia. For 

the reporting period ending on July 31, 2022, 

Camden County Municipal Utilities Authority 

discharged an average of 35 mg/L of ammonia. 

Source: U.S. Environmental Protection Agency. 

Integrated Compliance Information System (ICIS). 

Database. Retrieved June 29, 2023. 

14Federal Register, Vol. 32, No. 48 (32 FR 4000). 

March 11, 1967. https://www.fisheries.noaa.gov/ 

s3//2022-12/4000-4002.pdf. 

15NOAA Fisheries. (2023a). Shortnose 

Sturgeon—Overview. https://www.fisheries.

noaa.gov/species/shortnose-sturgeon. 

16 Id.; NOAA Fisheries. (2023b). Shortnose 

Sturgeon—Populations. https://www.fisheries.

noaa.gov/species/shortnose-sturgeon#populations. 

17Federal Register, Vol. 77, No. 24. February 6, 

2012. 77 FR 5879. https://www.federalregister.gov/ 

documents/2012/02/06/2012-1946/endangeredand-threatened-wildlife-and-plants-threatened-andendangered-status-for-distinct. 

18Federal Register, Vol. 82, No. 158 (82 FR 

39160). August 17, 2017. 50 CFR part 226. https:// 

www.federalregister.gov/documents/2017/08/17/ 

2017-17207/endangered-and-threatened-speciesdesignation-of-critical-habitat-for-the-endangerednew-york-bight. 

19National Marine Fisheries Service. (2022). New 

York Bight Distinct Population Segment of Atlantic 

Sturgeon (Acipenser oxyrinchus oxyrinchus), 5-Year 

Review: Summary and Evaluation. February 17, 

2022. https://www.fisheries.noaa.gov/resource/ 

document/new-york-bight-distinct-populationsegment-atlantic-sturgeon-5-year-review. 

20 Ibid. See Section 2.3.2, ‘‘Five-Factor Analysis 

(threats, conservation measures, and regulatory 

mechanisms)’’, A. through E., pp. 14–25. 

21 Dunton, K.J., Jordaan, A., Conover, D.O., 

McKown, K.A., Bonacci, L.A., and Frisk, M.G. 

(2015). Marine Distribution and Habitat Use of 

Atlantic Sturgeon in New York Lead to Fisheries 

Interactions and Bycatch. Marine and Coastal 

Fisheries 7:18–32. https://doi.org/10.1080/

19425120.2014.986348; Atlantic Sturgeon Bycatch 

Working Group. (2022). Action Plan to Reduce 

Atlantic Sturgeon Bycatch in Federal Large Mesh 

Gillnet Fisheries. NOAA National Marine Fisheries 

Service. https://media.fisheries.noaa.gov/2022-09/ 

Final-Action-Plan-to-Reduce-Atlantic-SturgeonBycatch.pdf. 

22Secor and Waldman (1999). 

23White, S.L., Sard, N.M., Brundage, H.M., 

Johnson, R.L., Lubinski, B.A., Eackles, M.S., Park, 

I.A., Fox, D.A., and Kazyak, D.C. (2022). Evaluating 

Sources of Bias in Pedigree-Based Estimates of 

Breeding Population Size. Ecological Applications 

32(5): e2602. https://doi.org/10.1002/eap.2602. 

24Federal Register, Vol. 82, No. 158 (82 FR 

39161). August 17, 2017. 50 CFR part 226. pp. 

39161–39163. https://www.federalregister.gov/ 

documents/2017/08/17/2017-17207/endangeredand-threatened-species-designation-of-criticalhabitat-for-the-endangered-new-york-bight. 

25 Ibid. p. 39162, see Dees (1961), Sulak and 

Clugston (1999), Billard and Lecointre (2001), Secor 

and Niklitschek (2002), and Pikitch et al. (2005), 

cited therein. 

26Stoklosa et al. (2018) ; Secor, D.H. and 

Niklitschek, E.J. (2001). Hypoxia and Sturgeons: 

Report to the Chesapeake Bay Program Dissolved 

Oxygen Criteria Team. March 29, 2001.Reference 

Number: [UMCES] CBL 01–0080. https://

www.researchgate.net/publication/277065759_

Hypoxia_and_Sturgeons_report_to_the_

Chesapeake_Bay_Program_Dissolved_Oxygen_

Criteria_Team. 

27Secor and Niklitschek (2001). Oxyregulation 

refers to an organism’s ability to maintain metabolic 

rates as the oxygen level in the water declines. 

28Secor, D., and T. Gunderson. (1998). Effects of 

hypoxia and temperature on survival, growth, and 

respiration of juvenile Atlantic sturgeon, Acipenser 

oxyrinchus. Fishery Bulletin 96:603–613.; 

Niklitschek, E. (2001). Bioenergetics modeling and 

assessment of suitable habitat for juvenile Atlantic 

and shortnose sturgeons (Acipenser oxyrinchus and 

A. brevirostrum) in the Chesapeake Bay. University 

of Maryland at College Park. 

29More information is available in the associated 

document, Technical Support Document for the 

Proposed Rule: Water Quality Standards to Protect 

Aquatic Life in the Delaware River. 

CSOs on sediment oxygen demand in 

the Delaware River has not been 

estimated, CSOs can over time increase 

or maintain sediment oxygen demand as 

untreated organic material settles on the 

riverbed and is broken down by oxygen 

consuming bacteria (thus, removing 

oxygen from the water column), a 

process that continues long after the end 

of an overflow event.9 CSOs have been 

a persistent source of pollutants in the 

specified zones of the Delaware River 

for over a century. For example, sewer 

overflows from Philadelphia in the early 

1900s deposited over 200,000 tons of 

solids per year, which, in combination 

with other solid wastes, created deposits 

12 feet deep in the river.10 From July 1, 

2021, to June 30, 2022, Philadelphia’s 

wastewater system alone discharged 

over 1.7 billion cubic feet of CSOs into 

the Delaware River.11

Although most point source 

discharges today are treated, treated 

effluent can still contain high levels of 

ammonia nitrogen, which depletes 

oxygen in the water as bacteria oxidize 

ammonia into nitrite, nitrate and 

dinitrogen gas.12 During the reporting 

periods from July through October 2022, 

major wastewater treatment facilities 

along the Delaware River discharged 

ammonia nitrogen at monthly average 

concentrations ranging from a low of 

0.07 milligrams nitrogen per liter (mgN/L) at the Florence Township Sewage 

Treatment Plant in New Jersey 

(discharging into Zone 2 of the Delaware 

River) to a high of 35 mg-N/L at the 

Camden County Municipal Utilities 

Authority in New Jersey (discharging 

into Zone 3 of the Delaware River).13

2. Endangered Species in the Specified 

Zones of the Delaware River 

The Delaware River is home to two 

oxygen-sensitive fish species— 

Shortnose Sturgeon and Atlantic 

Sturgeon—that are protected under the 

Federal Endangered Species Act (ESA). 

All populations of Shortnose Sturgeon 

were listed as endangered in 1967.14

Across the U.S., Shortnose Sturgeon 

face ongoing threats due to water 

pollution, habitat degradation, and 

fisheries bycatch, among other factors.15

While the historic population size of 

Shortnose Sturgeon in the Delaware 

River remains unknown, in 2006 the 

population was estimated to be 

approximately 12,000 adults.16 The 

New York Bight distinct population 

segment (DPS) of Atlantic Sturgeon— 

which includes the population found in 

the Delaware River—was listed as 

endangered under the ESA in 2012.17 In 

2017, the National Oceanic and 

Atmospheric Administration (NOAA 

Fisheries) designated the Delaware 

River, among others, as critical habitat 

for the New York Bight DPS of Atlantic 

Sturgeon,18 and reaffirmed its 

endangered listing in 2022 following a 

five-year review of its status.19 The 

remnant population of the New York 

Bight DPS of Atlantic Sturgeon faces 

ongoing threats due to water quality in 

natal rivers, such as the Delaware River, 

as well as climate change, ship strikes, 

fisheries bycatch, habitat loss, and 

entanglement in fishing gear.20 21 Like 

the Shortnose Sturgeon, the historic 

population size of Atlantic Sturgeon is 

not well documented. However, in 

1890, when the population was already 

declining, there were approximately 

180,000 female Atlantic Sturgeon in the 

Delaware River.22 Despite 

improvements in dissolved oxygen 

levels since the 1970s, it is estimated 

that only 125–250 adult Atlantic 

Sturgeon currently return to spawn in 

the Delaware River.23

In addition to being listed as 

endangered under the ESA, available 

evidence suggests that Shortnose 

Sturgeon and Atlantic Sturgeon are the 

most oxygen-sensitive species in the 

specified zones of the Delaware River. 

In general, all sturgeon species share 

common life history traits,24 among 

which they are recognized to be 

relatively more sensitive to low 

dissolved oxygen levels compared to 

other co-occurring fish.25 26 Sturgeons 

are considered unusually sensitive to 

hypoxia given their documented 

metabolic and behavioral responses and 

limited ability to oxyregulate.27 Juvenile 

Atlantic Sturgeon are particularly 

sensitive to low dissolved oxygen levels, 

especially at high water temperatures,28

such as those typically present at the 

peak of summer in the Delaware River.29

A literature review across oxygenVerDate Sep<11>2014 16:23 Dec 20, 2023 Jkt 262001 PO 00000 Frm 00048 Fmt 4702 Sfmt 4702 E:\FR\FM\21DEP1.SGM 21DEP1

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30Stoklosa et al. (2018). 31National Marine Fisheries Service (2022). See 

Section 2.3.2.1, ‘‘Present or threatened destruction, 

modification, or curtailment of its habitat or range.’’ 32 Ibid. See Allen et al. (2014), cited therein. 33 Ibid. See Moberg and DeLucia (2016), Stetzar et 

al. (2015), and Park (2020), cited therein. 34Sharp, J. (2010). Estuarine oxygen dynamics: 

What can we learn about hypoxia from long-time 

records in the Delaware estuary? Limnology and 

Oceanography, 55(2), 535–548. 

35Sharp (2010). 

36Shoda, M.E., and Murphy, J.C. (2022). Waterquality trends in the Delaware River Basin 

calculated using multisource data and two methods 

for trend periods ending in 2018. U.S. Geological 

Survey Scientific Investigations Report 2022–5097. 

https://doi.org/10.3133/sir20225097. 

37More information is available in the associated 

document, Technical Support Document for the 

Proposed Rule: Water Quality Standards to Protect 

Aquatic Life in the Delaware River; Delaware River 

Basin Commission (2022a); Niklitschek, E., and D. 

Secor. (2009a). Dissolved oxygen, temperature and 

salinity effects on the ecophysiology and survival 

of juvenile Atlantic sturgeon in estuarine waters: I. 

Laboratory results. Journal of Experimental Marine 

Biology and Ecology 381:S150–S160. https://

doi.org/10.1016/j.jembe.2009.07.018; Stoklosa et al. 

(2018). 

38 Delaware River Basin Commission (2022a, 

2022b). 

39Although portions of the Delaware River 

Estuary are within New York’s jurisdiction, the 

EPA’s proposed rulemaking is not applicable to 

waters under New York’s jurisdiction (see section 

IV.A. of this preamble: Scope of EPA’s Proposed 

Rule). Therefore, the EPA does not discuss New 

York’s WQS further in this proposed rulemaking. 

40 DRBC was established pursuant to Federal law 

(75 Stat. 688 (1961)). 

41 Delaware River Basin Compact, art. 1, ‘‘Short 

Title, Definitions, Purpose and Limitations,’’ 

§ 1.3(a), (b), & (c) ‘‘Purpose and Findings,’’ pp. 3 & 

4, and art. 5, ‘‘Pollution Control,’’ § 5.5(b), ‘‘Further 

Jurisdiction,’’ p. 11, (1961), available at https://

www.nj.gov/drbc/library/documents/compact.pdf. 

42 Delaware River Basin Compact, art. 5, 

‘‘Pollution Control,’’ § 5.2, ‘‘Policy and Standards,’’ 

p. 11 (1961), available at https://www.nj.gov/drbc/ 

library/documents/compact.pdf (DRBC ‘‘may adopt 

and from time to time amend and repeal rules, 

regulations and standards to control . . . future 

pollution and abate existing pollution’’). DRBC, the 

states, and the EPA refer to these rules, regulations, 

and standards as equivalent to WQS under the 

CWA. As such, the term WQS is used herein to refer 

to these rules, regulations, and standards. 

43 Delaware River Basin Commission. (2013). 

Delaware River Basin Water Code. https://

www.nj.gov/drbc/library/documents/watercode.pdf. 

44A map showing the Delaware River watershed 

and the specified zones is available in the docket 

(Docket ID No. EPA–HQ–OW–2023–0222) as well 

as in each of the support documents associated with 

this rule: Technical Support Document for the 

Proposed Rule: Water Quality Standards to Protect 

Aquatic Life in the Delaware River; Economic 

Analysis for the Proposed Rule: Water Quality 

Standards to Protect Aquatic Life in the Delaware 

River; and Environmental Justice Analysis for the 

Proposed Rule: Water Quality Standards to Protect 

Aquatic Life in the Delaware River. 

sensitive species in the Delaware River 

indicates that Atlantic Sturgeon, 

particularly the juvenile life stage, have 

the highest documented dissolved 

oxygen requirements for growth and 

survival when compared to other 

oxygen-sensitive species in the specified 

zones of the Delaware River.30 In its 

five-year review of the listing of the 

New York Bight DPS of Atlantic 

Sturgeon, NOAA Fisheries observed a 

continuation of low dissolved oxygen 

conditions in the Delaware River around 

the expected location of age 0–1 

Atlantic Sturgeon.31 Low oxygen levels 

can lead to habitat displacement effects 

whereby juvenile Atlantic Sturgeon 

seeking relief are constrained to waters 

that remain suboptimal for growth due 

to other limiting factors (e.g., higher 

salinity waters).32 NOAA Fisheries also 

noted studies linking age 0–1 Atlantic 

Sturgeon capture rates in the fall to the 

preceding summer dissolved oxygen 

conditions in the Delaware River, 

providing further evidence that low 

dissolved oxygen levels are a 

contributor to the mortality of juvenile 

Atlantic Sturgeon.33

3. Dissolved Oxygen Trends in the 

Specified Zones of the Delaware River 

Dissolved oxygen levels in Zone 3, 

Zone 4, and the upper portion of Zone 

5 of the Delaware River mirror trends in 

historic pollutant loading and recent 

pollution control efforts in the river. 

Average summer dissolved oxygen 

levels in the Delaware River near 

Chester, Pennsylvania (Zone 4) declined 

from near saturation in the late 1880s to 

near zero (i.e., anoxia) in the 1950s and 

1960s.34 Starting in 1970, dissolved 

oxygen levels began to increase steadily 

in association with declining ammonia 

nitrogen concentrations in the river.35

Reductions in nutrient concentrations, 

including ammonia nitrogen, have been 

documented across the Delaware River 

watershed through at least 2018.36

However, dissolved oxygen levels in the 

summer remain low enough to limit the 

growth and survival of oxygen-sensitive 

species and life stages, such as juvenile 

Atlantic Sturgeon.37 Recent modeling 

studies have shown that further 

reductions in pollutant loading, 

including a reduction in the volume and 

frequency of CSOs as well as enhanced 

treatment of ammonia nitrogen 

discharges, could significantly improve 

the dissolved oxygen conditions in the 

relevant zones of the Delaware River.38

C. Administration of Water Quality 

Standards in the Delaware River 

In 1961, the Delaware River Basin 

Compact established the Delaware River 

Basin Commission (DRBC), comprised 

of the states of Delaware, New Jersey, 

New York,39 and Pennsylvania and the 

Federal Government, to jointly manage 

the Delaware River Basin’s water 

resources.40 Through DRBC, each state 

participates in the shared governance of 

this regional resource and maintains 

sovereign rights over the portion of the 

river within its jurisdiction.41

Pursuant to the Delaware River Basin 

Compact, DRBC adopts WQS for 

interstate waters, including the 

Delaware River Estuary.42 However as 

noted above, under the CWA, states 

have the primary responsibility for 

reviewing, establishing, and revising 

WQS applicable to their waters, and 

must submit new or revised WQS to the 

EPA for review and approval or 

disapproval. 

Given the unique interjurisdictional 

management of the Delaware River 

Estuary, WQS are submitted to the EPA 

for review through a process 

coordinated across the state, regional, 

and Federal levels. This process begins 

when DRBC adopts WQS for the 

Delaware River Estuary. To comply with 

CWA section 303(c), the Estuary states 

of Delaware, New Jersey, and 

Pennsylvania have provisions in their 

state WQS regulations that explicitly 

reference or implicitly incorporate 

DRBC’s WQS as the applicable WQS for 

the portions of the river under their 

jurisdictions. When DRBC adopts new 

or revised WQS, each relevant member 

state submits a certification to the EPA 

from that state’s attorney general or 

other appropriate legal authority, in 

accordance with 40 CFR 131.6(e). Those 

certifications provide that DRBC’s new 

or revised WQS were duly adopted 

pursuant to state law. The EPA then 

reviews whether those WQS are 

consistent with the CWA and the EPA’s 

implementing regulation and approves 

or disapproves them. 

D. Currently Applicable Aquatic Life 

Designated Uses and Dissolved Oxygen 

Criteria 

In 1967, DRBC adopted WQS for the 

zones of the Delaware River included in 

this proposed rule.43 Based on the 

conditions of the Delaware River at the 

time, DRBC concluded that 

‘‘propagation of fish’’ was not attainable 

for Zone 3, Zone 4, and the upper 

portion of Zone 5 (in total, river miles 

108.4 to 70.0) of the Delaware River 

(hereafter, referred to as ‘‘specified 

zones’’ or ‘‘relevant zones’’),44 due to 

the presence of industrial and 

municipal discharges and associated 

low dissolved oxygen levels. DRBC, 

therefore, adopted WQS to include 

‘‘maintenance of resident fish and other 

aquatic life,’’ ‘‘passage of anadromous 

fish,’’ and a dissolved oxygen criterion 

of 3.5 mg/L, as a daily average, for these 


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45 Delaware River Basin Commission. (2015). 

‘‘Existing Use Evaluation for Zones 3, 4, & 5 of the 

Delaware Estuary Based on Spawning and Rearing 

of Resident and Anadromous Fishes.’’ September 

30, 2015. https://www.state.nj.us/drbc/library/ 

documents/ExistingUseRpt_zones3-5_sept2015.pdf. 46Anadromous fish are species that are born and 

reared as juveniles in freshwater, migrate to marine 

waters where they spend most of their adult lives, 

and return to their natal, freshwater rivers to spawn. 

zones of the Delaware River.45 46

Because these WQS provide for the 

‘‘maintenance’’ and ‘‘passage’’ of aquatic 

life (i.e., ‘‘protection’’) but not the 

‘‘propagation of fish, shellfish and 

wildlife,’’ these WQS are not consistent 

with the goals specified in CWA section 

101(a)(2). However, these WQS adopted 

in 1967 remain applicable for Zone 3, 

Zone 4, and the upper portion of Zone 

5 of the Delaware River as directly 

referred to or implicitly incorporated in 

Delaware’s, New Jersey’s, and 

Pennsylvania’s WQS. 

1. Delaware’s, New Jersey’s, and 

Pennsylvania’s Current Aquatic Life 

Designated Uses 

As described in section III.C. of this 

preamble, Delaware, New Jersey, and 

Pennsylvania each has its own WQS for 

the specified zones of the Delaware 

River under its jurisdiction. Delaware’s 

current aquatic life designated use for 

the specified zones of the Delaware 

River includes all life stages, thus 

including the propagation component of 

the CWA section 101(a)(2) use. New 

Jersey’s aquatic life designated use for 

the specified zones of the Delaware 

River incorporate by reference the 

designated uses in DRBC’s Water 

Quality Regulations. Pennsylvania’s 

aquatic life designated uses for the 

specified zones of the Delaware River 

align with DRBC’s ‘‘maintenance’’ and 

‘‘passage’’ designated use (Table 2 of 

this preamble). Therefore, neither New 

Jersey’s nor Pennsylvania’s aquatic life 

designated use for the specified zones of 

the Delaware River include the 

propagation component of the CWA 

section 101(a)(2) use. 

TABLE 2—CURRENT AQUATIC LIFE DESIGNATED USES IN ZONE 3, ZONE 4, AND UPPER-ZONE 5 OF THE DELAWARE RIVER

Entity Designated use 

DRBC 1 .................... Maintenance of resident fish and other aquatic life, passage of anadromous fish, wildlife. 

Delaware 2 ............... Fish, Aquatic Life & Wildlife.3

New Jersey 4 ........... The designated uses for the mainstem Delaware River and Delaware Bay are those contained in the DRBC Water Quality 

Regulations. 

Pennsylvania 5 ........ Warm Water Fishes (Maintenance Only); Migratory fishes (Passage Only).6

1 Delaware River Basin Commission. ‘‘Administrative Manual—Part III Water Quality Regulations with Amendments Through December 7,

2022.’’ Accessed May 3, 2023. https://www.nj.gov/drbc/library/documents/WQregs.pdf. 2 Delaware Administrative Code. ‘‘7401 Surface Water Quality Standards.’’ Title 7 Natural Resources & Environmental Control. Delaware Department of Natural Resource and Environmental Control. Accessed May 3, 2023. https://regulations.delaware.gov/AdminCode/title7/7000/7400/ 

7401.pdf. 3 Delaware defines Fish, Aquatic Life & Wildlife as, ‘‘all animal and plant life found in Delaware, either indigenous or migratory, regardless of 

life stage or economic importance.’’ A footnote specifies that this use includes shellfish propagation. 4 New Jersey Administrative Code. ‘‘N. J. A. C. 7:9B Surface Water Quality Standards.’’ Accessed May 3, 2023. https://dep.nj.gov/wp-content/ 

uploads/rules/rules/njac7_9b.pdf. 5Pennsylvania Code. ‘‘Chapter 93. Water Quality Standards.’’ Commonwealth of Pennsylvania. Accessed May 3, 2023. https://

www.pacodeandbulletin.gov/secure/pacode/data/025/chapter93/025_0093.pdf. 6Pennsylvania defines its ‘‘Warm Water Fishes’’ designated use as, ‘‘Maintenance and propagation of fish species and additional flora and 

fauna which are indigenous to a warm water habitat’’ and defines its ‘‘Migratory Fishes’’ designated use as, ‘‘Passage, maintenance and propagation of anadromous and catadromous fishes and other fishes which move to or from flowing waters to complete their life cycle in other 

waters.’’ For the specified zones of the Delaware River, Pennsylvania excluded propagation from the designated uses by specifying ‘‘Maintenance Only’’ and ‘‘Passage Only’’ in parentheses. 

2. Delaware’s, New Jersey’s, and 

Pennsylvania’s Current Dissolved 

Oxygen Criteria 

For dissolved oxygen in the relevant 

zones, all three states incorporate 

DRBC’s water quality criteria by 

reference; therefore, DRBC’s dissolved 

oxygen criteria are the applicable 

criteria for the relevant zones in each 

state (Table 3 of this preamble). As 

explained above with respect to the 

aquatic life designated use, DRBC’s 

dissolved oxygen criteria for the 

specified zones of the Delaware River do 

not protect for aquatic life propagation 

and are therefore not consistent with 

CWA section 101(a)(2) goals. 

TABLE 3—CURRENT DISSOLVED OXYGEN CRITERIA IN ZONE 3, ZONE 4, AND UPPER-ZONE 5 OF THE DELAWARE RIVER

Entity Dissolved oxygen aquatic life criteria 

DRBC 1 .................... 24-hour average concentration shall not be less than 3.5 mg/l. During the periods from April 1 to June 15, and September 

16 to December 31, the dissolved oxygen shall not have a seasonal average less than 6.5 mg/l in the entire zone. 

Delaware 2 ............... For waters of the Delaware River and Delaware Bay, duly adopted Delaware River Basin Commission (DRBC) Water 

Quality Regulations shall be the applicable criteria. 

New Jersey 3 ........... For parameters with criteria in the DRBC Water Quality Regulations, the criteria contained therein are the applicable criteria. 

Pennsylvania 4 ........ See DRBC Water Quality Regulations. 

1 Delaware River Basin Commission. ‘‘Administrative Manual—Part III Water Quality Regulations with Amendments Through December 7,

2022.’’ Accessed May 3, 2023. https://www.nj.gov/drbc/library/documents/WQregs.pdf. 2 Delaware Administrative Code. ‘‘7401 Surface Water Quality Standards.’’ Title 7 Natural Resources & Environmental Control. Delaware Department of Natural Resource and Environmental Control. Accessed May 3, 2023. https://regulations.delaware.gov/AdminCode/title7/7000/7400/

7401.pdf. 3 New Jersey Administrative Code. ‘‘N. J. A. C. 7:9B Surface Water Quality Standards.’’ Accessed May 3, 2023. https://dep.nj.gov/wp-content/ 

uploads/rules/rules/njac7_9b.pdf. 4Pennsylvania Code. ‘‘Chapter 93. Water Quality Standards.’’ Commonwealth of Pennsylvania. Accessed May 3, 2023. https://

www.pacodeandbulletin.gov/secure/pacode/data/025/chapter93/025_0093.pdf. 


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47 December 1, 2022. Letter from Radhika Fox, 

Assistant Administrator, EPA Office of Water, to 

Steven J. Tambini, Executive Director, Delaware 

River Basin Commission; Shawn M. Garvin, 

Secretary, Delaware Department of Natural 

Resources and Environmental Control; Shawn M. 

LaTourette, Commissioner, New Jersey Department 

of Environmental Protection; and Ramez Ziadeh, 

Acting Secretary, Pennsylvania Department of 

Environmental Protection. 

48The EPA’s Administrator’s Determination 

stated, ‘‘EPA is determining [. . . that] revised 

aquatic life designated uses that provide for 

propagation of fish, consistent with CWA section 

101(a)(2) and 40 CFR 131.20(a) [. . .] are necessary 

for zone 3, zone 4, and the upper portion of zone 

5 (in total, river miles 108.4 to 70.0) of the Delaware 

River Estuary, to meet the requirements of the 

CWA.’’ 

49 December 1, 2022. Letter from Radhika Fox, 

Assistant Administrator, EPA Office of Water, to 

Steven J. Tambini, Executive Director, Delaware 

River Basin Commission; Shawn M. Garvin, 

Secretary, Delaware Department of Natural 

Resources and Environmental Control; Shawn M. 

LaTourette, Commissioner, New Jersey Department 

of Environmental Protection; and Ramez Ziadeh, 

Acting Secretary, Pennsylvania Department of 

Environmental Protection. 

3. Intersection of Delaware’s, New 

Jersey’s, and Pennsylvania’s Current 

Aquatic Life Designated Uses and 

Dissolved Oxygen Criteria With CWA 

101(a)(2) Goals 

Table 4 of this preamble provides a 

summary outlining whether Delaware’s, 

New Jersey’s, and Pennsylvania’s 

current aquatic life designated uses 

align with CWA section 101(a)(2) goals 

and whether each state’s current 

dissolved oxygen criteria are protective 

of an aquatic life designated use that 

includes propagation. As explained 

above, Delaware is the only state that 

includes aquatic life propagation in its 

designated uses for the specified zones 

of the Delaware River. However, none of 

the three states’ dissolved oxygen water 

quality criteria for the specified zones 

are protective of fish and shellfish 

propagation. Therefore, none of the 

states, and by extension none of the 

specified zones of the Delaware River, 

currently has a set of WQS for aquatic 

life that are fully consistent with the 

CWA section 101(a)(2) goals (i.e., ‘‘water 

quality which provides for the 

protection and propagation of fish, 

shellfish, and wildlife [. . .]’’). 

TABLE 4—INTERSECTION OF DELAWARE’S, NEW JERSEY’S, AND PENNSYLVANIA’S CURRENT AQUATIC LIFE DESIGNATED

USES AND DISSOLVED OXYGEN CRITERIA WITH CWA 101(a)(2) GOALS

State Applicable zone(s) 

Designated use includes CWA 

section 101(a)(2) propagation 

component 

Dissolved oxygen criteria 

protective of aquatic life 

propagation 

Delaware ........................................ Upper-5 ......................................... Yes ................................................ No. 

New Jersey .................................... 3, 4, Upper-5 ................................ No ................................................. No. 

Pennsylvania .................................. 3, 4 ................................................ No ................................................. No. 

E. Summary of the EPA’s 

Administrator’s Determination 

On December 1, 2022, the EPA 

determined that the CWA section 

101(a)(2) use of propagation is now 

attainable and therefore revised WQS 

are necessary to protect aquatic life in 

certain water quality management zones 

of the Delaware River.47 Specifically, 

the EPA issued an Administrator’s 

Determination, pursuant to CWA 

section 303(c)(4)(B), finding that a 

revised designated use to protect aquatic 

life propagation and corresponding 

dissolved oxygen criteria to protect that 

use are necessary in Zone 3, Zone 4, and 

the upper portion of Zone 5 (in total, 

river miles 108.4 to 70.0) of the 

Delaware River. The Administrator’s 

Determination can be accessed at 

https://www.epa.gov/wqs-tech/federallypromulgated-water-quality-standardsspecific-states-territories-and-tribes. 

IV. Proposed Water Quality Standards 

A. Scope of EPA’s Proposed Rule 

In accordance with the 

Administrator’s Determination, the 

EPA’s proposed rule, if finalized, would 

apply to Zone 3, Zone 4, and the upper 

portion of Zone 5 of the Delaware River 

(in total, river miles 108.4 to 70.0), for 

the states of Delaware, New Jersey, and 

Pennsylvania (Table 5 of this preamble). 

TABLE 5—ZONES OF THE DELAWARE RIVER COVERED BY THE EPA’S PROPOSED RULE

Segment of the Delaware River River miles States affected 

Zone 3 ............................................................... 108.4 to 95.0 .................................................... New Jersey, Pennsylvania. 

Zone 4 ............................................................... 95.0 to 78.8 ...................................................... New Jersey, Pennsylvania. 

Zone 5—Upper Portion ..................................... 78.8 to 70.0 ...................................................... Delaware, New Jersey. 

B. Proposed Aquatic Life Designated 

Use 

The EPA is proposing to promulgate 

a revised aquatic life designated use for 

the specified zones of the Delaware 

River to meet the CWA section 101(a)(2) 

goals (i.e., ‘‘water quality which 

provides for the protection and 

propagation of fish, shellfish, and 

wildlife’’), as specified in the EPA’s 

Administrator’s Determination.48

Although the relevant zones of the 

Delaware River are each under the 

jurisdiction of two or more states (Table 

5 of this preamble), CWA section 303(c) 

assigns the individual states the role of 

adopting WQS. Therefore, the EPA is 

evaluating the aquatic life uses on a 

state-by-state basis. 

As explained in section III.D. of this 

preamble, Delaware’s ‘‘Fish, Aquatic 

Life & Wildlife’’ designated use includes 

all life stages of indigenous and 

migratory organisms; therefore, 

Delaware’s aquatic life designated use in 

the specified zones under its 

jurisdiction is already consistent with 

the CWA section 101(a)(2) goals and no 

revisions to Delaware’s aquatic life 

designated use are necessary to meet 

CWA requirements. In contrast, New 

Jersey’s and Pennsylvania’s aquatic life 

designated uses for the relevant zones of 

the Delaware River under their 

jurisdiction do not include 

‘‘propagation’’ and are therefore not 

consistent with CWA section 101(a)(2) 

goals. As explained in section III.E. of 

this preamble, the EPA determined that 

propagation is now an attainable use in 

the specified zones of the Delaware 

River.49 Therefore, for the portions of 

the specified zones under New Jersey’s 

and Pennsylvania’s jurisdiction, a 


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50United States Environmental Protection 

Agency. (1986). Quality Criteria for Water 1986. 

Document ID: EPA 440/5–86–001. May 1, 1986. 

https://www.epa.gov/sites/default/files/2018-10/ 

documents/quality-criteria-water-1986.pdf. 

51United States Environmental Protection 

Agency. (2000). Ambient Aquatic Life Water 

Quality Criteria for Dissolved Oxygen (Saltwater): 

Cape Cod to Cape Hatteras. Document ID: EPA– 

822–R–00–012. November 2000. https://

www.epa.gov/sites/default/files/2018-10/ 

documents/ambient-al-wqc-dissolved-oxygen-capecode.pdf. 

52 Id. Page 41. 

53Stoklosa et al. (2018); Delaware River Basin 

Commission (2015); Moberg, T. and M. DeLucia. 

(2016). Potential Impacts of Dissolved Oxygen, 

Salinity and Flow on the Successful Recruitment of 

Atlantic Sturgeon in the Delaware River. The 

Nature Conservancy. Harrisburg, PA. https://

www.conservationgateway.org/Conservation

Practices/Freshwater/HabitatProtection

andRestoration/Documents/DelawareAtlantic

SturgeonReport_TNC5172016.pdf. 

54Moberg and DeLucia. (2016). 

55This conclusion was based on results of the 

growth model, described in sections 3.3.3 and 4.1.2 

of the associated document, Technical Support 

Document for the Proposed Rule: Water Quality 

Standards to Protect Aquatic Life in the Delaware 

River. 

revised aquatic life designated use that 

includes propagation is necessary to 

meet CWA requirements and ensure that 

the specified zones of the Delaware 

River are consistent with CWA section 

101(a)(2) goals. 

Thus, the EPA is proposing to 

promulgate an aquatic life designated 

use for Zone 3, Zone 4, and the upper 

portion of Zone 5 of the Delaware River 

(in total, river miles 108.4 to 70.0) for 

the states of New Jersey and 

Pennsylvania, as follows: Protection and 

propagation of resident and migratory 

aquatic life. 

C. Dissolved Oxygen Criteria To Protect 

Aquatic Life Propagation 

The EPA is proposing to establish 

dissolved oxygen criteria—derived from 

the latest sound scientific information— 

for Delaware, New Jersey, and 

Pennsylvania, for the specified zones of 

the Delaware River. The proposed 

dissolved oxygen criteria would protect 

the EPA’s proposed designated use for 

New Jersey and Pennsylvania, as well as 

Delaware’s current aquatic life 

designated use for the specified zones. 

1. Derivation of Dissolved Oxygen 

Criteria 

To derive protective dissolved oxygen 

criteria for the specified zones of the 

Delaware River, the EPA used methods 

adapted from peer-reviewed literature 

and data from laboratory studies 

relevant to oxygen-sensitive sturgeon 

species in the Delaware River. Although 

the methods and data are from peerreviewed scientific literature, the EPA is 

nonetheless in the process of 

completing an external peer review on 

the application of these methods and 

data in this context where the EPA is 

proposing criteria to protect proposed 

and applicable aquatic life designated 

uses that include propagation. This 

section presents a summary of the data 

and methods that the EPA used to 

derive protective dissolved oxygen 

criteria for this proposed rulemaking. 

First, the EPA describes the Agency’s 

existing dissolved oxygen national 

recommendations and guidance 

documents. Then, the EPA explains 

how the Agency selected three seasons 

to derive criteria protective of oxygensensitive species in the relevant zones of 

the Delaware River. Next, the EPA 

details an Atlantic Sturgeon cohort 

model used to derive criteria protective 

of juvenile Atlantic Sturgeon during the 

season associated with their growth and 

development. After that, the EPA 

explains how criteria were developed to 

protect oxygen-sensitive species during 

the other two seasons. Lastly, the EPA 

concludes with an explanation for 

proposing criteria expressed as percent 

oxygen saturation, rather than as 

concentration. This section is intended 

to be a high-level summary of the EPA’s 

criteria derivation methods and results 

for this proposed rulemaking. More 

details and information are available in 

the associated technical support 

document, Technical Support 

Document for the Proposed Rule: Water 

Quality Standards to Protect Aquatic 

Life in the Delaware River. The EPA will 

consider information received during 

the public comment period (detailed 

above), in addition to the external peer 

review of the technical support 

document, and accordingly may make 

changes to the proposed criteria for a 

final rule. 

Existing the EPA Methodology and 

Guidance Documents 

Under CWA section 304(a), the EPA 

publishes, from time to time, national 

recommended aquatic life criteria for a 

variety of pollutants and parameters. 

The EPA’s national recommended 

criteria for dissolved oxygen in 

freshwater and saltwater environments 

are from the 1986 Quality Criteria for 

Water (‘‘Gold Book’’) 50 and the 2000 

Ambient Aquatic Life Water Quality 

Criteria for Dissolved Oxygen 

(Saltwater): Cape Cod to Cape Hatteras 

(‘‘Virginian Province Document’’),51

respectively. The EPA’s 

recommendations in the Virginian 

Province Document state that, ‘‘in cases 

where a threatened or endangered 

species occurs at a site, and sufficient 

data exist to suggest that it is more 

sensitive at concentrations above the 

criteria, it is appropriate to consider 

development of site-specific criteria 

based on this species.’’ 52 As explained 

previously in section III.B. of this 

preamble, Atlantic Sturgeon and 

Shortnose Sturgeon are federally listed 

as endangered under the ESA and are 

uniquely sensitive to hypoxia. Given the 

availability of laboratory data specific to 

the oxygen requirements of Atlantic 

Sturgeon and Shortnose Sturgeon, the 

EPA chose to derive site-specific criteria 

to protect the oxygen-sensitive 

endangered species in the specified 

zones of the Delaware River and not rely 

on the national recommendations in the 

Gold Book or Virginian Province 

Document in this instance. 

Delineating Seasons for Criteria 

Derivation 

In consideration of available 

information, including information 

developed by DRBC, the EPA is 

proposing to delineate three distinct 

seasons for dissolved oxygen criteria 

development that are intended to 

protect Atlantic Sturgeon early life 

stages, while also protecting a range of 

other aquatic species’ sensitive life 

stages in the specified zones. The EPA 

is proposing to define the Spawning and 

Larval Development season as occurring 

from March 1 to June 30, which 

generally covers spawning and egg and 

larval development periods for many 

oxygen-sensitive species, including 

Atlantic Sturgeon, Shortnose Sturgeon, 

American Shad, Atlantic Rock Crab, 

Channel Catfish, Striped Bass, 

Largemouth Bass, White Perch, and 

Yellow Perch.53 The EPA is proposing 

to define the Juvenile Development 

season as occurring from July 1 to 

October 31 and the Overwintering 

season as occurring from November 1 to 

February 28/29, based on young-of-theyear juvenile Atlantic Sturgeon growth 

rates.54 By November, growth rates are 

reduced by low water temperatures 

despite relatively high levels of 

dissolved oxygen.55 While the EPA is 

proposing to define seasons largely 

based on the early life stages of Atlantic 

Sturgeon, the proposed seasons also 

generally correspond with early life 

stages of other oxygen-sensitive species 

in the specified zones of the Delaware 

River. By developing criteria that are 

protective of Atlantic Sturgeon, which, 

as described in section III.B. of this 

preamble, is the most oxygen-sensitive 

species in the relevant zones of the 

Delaware River, the EPA concluded that 

the criteria would also be protective of 

other less oxygen-sensitive resident and 


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56Campbell, J., and L. Goodman. (2004). Acute 

sensitivity of juvenile shortnose sturgeon to low 

dissolved oxygen concentrations. Transactions of 

the American Fisheries Society 133:722–776; 

Niklitschek, E., and D. Secor. (2009a). Dissolved 

oxygen, temperature and salinity effects on the 

ecophysiology and survival of juvenile Atlantic 

sturgeon in estuarine waters: I. Laboratory results. 

Journal of Experimental Marine Biology and 

Ecology 381:S150–S160. https://doi.org/10.1016/

j.jembe.2009.07.018; United States Environmental 

Protection Agency. (2003). Ambient Water Quality 

Criteria for Dissolved Oxygen, Water Clarity and 

Chlorophyll a for the Chesapeake Bay and its Tidal 

Tributaries. Document ID: EPA 903–R–03–002. 

April 2003. https://nepis.epa.gov/Exe/ZyPDF.cgi/

P100YKPQ.PDF?Dockey=P100YKPQ.PDF; 

Niklitschek, E.J., and D.H. Secor. (2005). Modeling 

spatial and temporal variation of suitable nursery 

habitats for Atlantic sturgeon in the Chesapeake 

Bay. Estuarine, Coastal and Shelf Science 64:135– 

148. https://doi.org/10.1016/j.ecss.2005.02.012; 

Niklitschek, E.J., and D.H. Secor. (2009b). Dissolved 

oxygen, temperature and salinity effects on the 

ecophysiology and survival of juvenile Atlantic 

sturgeon in estuarine waters: II. Model development 

and testing. Journal of Experimental Marine Biology 

and Ecology 381:S161–S172. https://doi.org/ 

10.1016/j.jembe.2009.07.019; USGS 01467200 

Delaware River at Penn’s Landing, Philadelphia, 

PA. Retrieved March 9, 2023. https://waterdata.

usgs.gov/nwis/inventory/?site_

no=01467200&agency_cd=USGS; USGS 01477050 

Delaware River at Chester PA. Retrieved January 31, 

2023. https://waterdata.usgs.gov/nwis/

inventory?agency_code=USGS&site_no=01477050; 

Park, I. (2023). State of Delaware Annual 

Compliance Report for Atlantic Sturgeon. Delaware 

Division of Fish and Wildlife, Department of 

Natural Resources and Environmental Control. 

September 2023. 

57Water temperature and salinity can affect the 

oxygen requirements of aquatic species and are 

needed to compute percent oxygen saturation, a 

measure of dissolved oxygen availability to aquatic 

organisms, from dissolved oxygen concentrations. 

58Experimental data are from Campbell and 

Goodman 2004, Niklitschek and Secor 2009a. 

59USGS 01467200 Delaware River at Penn’s 

Landing, Philadelphia, PA. Retrieved March 9, 

2023. https://waterdata.usgs.gov/nwis/inventory/ 

?site_no=01467200&agency_cd=USGS; USGS 

01477050 Delaware River at Chester, PA. Retrieved 

January 31, 2023. https://waterdata.usgs.gov/nwis/

inventory?agency_code=USGS&site_no=01477050; 

Park (2023). 

60E.g., Woodland, R.J., Secor, D.H., and 

Niklitschek, E.J. (2009). Past and Future Habitat 

Suitability for the Hudson River Population of 

Shortnose Sturgeon: A Bioenergetic Approach to 

Modeling Habitat Suitability for an Endangered 

Species. American Fisheries Society Symposium 

69: 589–604; Collier, J.J., Chiotti, J.A., Boase, J., 

Mayer, C.M., Vandergoot, C.S., and Bossenbroek, 

J.M. (2022). Assessing habitat for lake sturgeon 

(Acipenser fulvescens) reintroduction to the 

Maumee River, Ohio using habitat suitability index 

models. Journal of Great Lakes Research. 48(1): 

219–228. https://doi.org/10.1016/j.jglr.2021.11.006; 

Brown, S.K., Buja, K.R., Jury, S.H., Monaco, M.E., 

and Banner, A. (2000). Habitat Suitability Index 

Models for Eight Fish and Invertebrate Species in 

Casco and Sheepscot Bays, Maine. North American 

Journal of Fisheries Management, 20(2): 408–435, 

https://doi.org/10.1577/1548-8675(2000)

020%3C0408:HSIMFE%3E2.3.CO;2. 

61A percentile (e.g., 10th percentile) is the 

dissolved oxygen level below which the 

corresponding fraction (e.g., 10%) of the daily 

dissolved oxygen values during the season falls 

below. In this case, the season is the Juvenile 

Development season (July 1–October 31). 

migratory aquatic species in the 

specified zones of the Delaware River. 

Ecological Modeling To Derive Criteria 

for the Juvenile Development Season 

The EPA obtained recent and highquality data from a variety of sources, 

described below and detailed in the 

associated technical support document, 

to evaluate oxygen requirements of 

Atlantic Sturgeon in each season. The 

EPA quantified water quality conditions 

in the specified zones of the Delaware 

River using recent and high-quality 

monitoring data from two locations in 

the Delaware River. Since the Atlantic 

Sturgeon was listed as an endangered 

species in 2012, there have been few 

recent studies documenting their 

oxygen requirements. However, 

available data on sturgeon growth and 

mortality from Campbell and Goodman 

(2004), Niklitschek and Secor (2009a), 

and EPA (2003), along with methods 

from Niklitschek and Secor (2005) and 

Niklitschek and Secor (2009b), water 

quality monitoring data, and juvenile 

Atlantic Sturgeon abundance data from 

the Delaware Department of Natural 

Resources and Environmental Control 

(DNREC) provided the EPA with 

sufficient data to establish quantitative 

relationships between age-0 juvenile 

sturgeon growth, mortality, and habitat 

suitability.56

The EPA followed the peer-reviewed 

cohort modeling approach of 

Niklitschek and Secor (2005) to evaluate 

the effects of temperature, salinity, and 

dissolved oxygen on the potential 

growth and mortality of a hypothetical 

cohort or group of juvenile Atlantic 

Sturgeon spawned during a single 

year.57 The cohort model uses growth 

and mortality rates to calculate the 

instantaneous daily production 

potential, or the instantaneous amount 

of biomass produced per unit of cohort 

biomass per day. The EPA used the 

cohort model to estimate the fraction of 

the cohort that survives from July 1 

through October 31 (i.e., the Juvenile 

Development season) and the relative 

change in biomass for the same period. 

As part of the cohort model, the EPA 

developed a new mortality model and 

implemented a peer-reviewed 

bioenergetics-based growth model 

described by Niklitschek and Secor 

(2009b) to predict the daily 

instantaneous mortality rate and growth 

rate, respectively, for members of the 

cohort. To develop a mortality model, 

the EPA fit a regression to experimental 

data to predict mortality resulting from 

low dissolved oxygen at any given 

temperature and percent oxygen 

saturation.58 Mortality rates of juvenile 

sturgeons increased with declining 

dissolved oxygen levels and increased at 

higher rates with both declining 

dissolved oxygen and increasing water 

temperature. The EPA validated the 

results of the mortality model by using 

observed water quality data to predict 

relative abundance of the Atlantic 

Sturgeon young-of-year cohort on 

October 31 and comparing those results 

to catch data from DNREC’s juvenile 

abundance surveys.59 The growth model 

takes a bioenergetic approach that 

accounts for temperature-controlled 

maximum metabolic rates that may be 

further limited by oxygen levels. Low 

oxygen levels limit overall metabolic 

rates and cause a shift in the allocation 

of available energy away from growth. 

Predicted growth rates reflect the 

balance between energy inputs and 

losses and are therefore reduced by low 

oxygen. Water quality monitoring data 

in the relevant zones of the Delaware 

River show that the lowest oxygen 

levels coincided with the highest water 

temperatures, resulting in lower growth 

rates than either condition would cause 

alone. 

Habitat Suitability Indices have been 

used in the context of fish-habitat 

relationships, conservation 

management, and habitat evaluation to 

quantify the capacity of a given habitat 

to support essential life functions (e.g., 

growth, survival, reproduction) of a 

selected species.60 For this proposed 

rulemaking, the EPA defined a Habitat 

Suitability Index (HSI) for Atlantic 

Sturgeon as the instantaneous daily 

production potential, which was 

calculated using the cohort model. HSI 

evaluates the combined effect of percent 

oxygen saturation, water temperature, 

and salinity on the potential growth and 

survival of juvenile Atlantic Sturgeon 

during the Juvenile Development 

season. The EPA used quantile 

generalized additive models (QGAMs) 

to quantify relationships between 

computed values of HSI in each year 

and corresponding seasonal percentiles 

of daily dissolved oxygen for that year.61

QGAMs can model the non-linear 

relationship between dissolved oxygen 

and HSI as well as predict the expected 

median HSI, rather than the expected 

mean. 

The EPA followed the approach of 

Niklitschek and Secor (2005) to define 

suitable habitat for juvenile Atlantic 

Sturgeon growth and survival as 

habitats with water quality resulting in 

HSI greater than zero. When HSI is less 

than or equal to zero, seasonal average 

mortality rates are greater than or equal 

to seasonal average growth rates and the 

overall biomass of the cohort is likely to 

decrease. Conversely, a cohort of 


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62Experimental data are from Campbell and 

Goodman 2004 and Niklitschek and Secor 2009a. 

63Niklitschek and Secor 2009a. 

64Stoklosa et al. (2018); United States 

Environmental Protection Agency. (2000). Ambient 

Aquatic Life Water Quality Criteria for Dissolved 

Oxygen (Saltwater): Cape Cod to Cape Hatteras. 

Document ID: EPA–822–R–00–012. November 2000. 

https://www.epa.gov/sites/default/files/2018-10/ 

documents/ambient-al-wqc-dissolved-oxygen-capecode.pdf. 

65Niklitschek and Secor (2009a, 2009b). 

66Percent oxygen saturation and dissolved 

oxygen concentration are two different ways to 

measure oxygen levels in water. Dissolved oxygen 

concentration is the amount of oxygen dissolved in 

the water, typically represented as milligrams of 

oxygen per liter of water. Percent oxygen saturation 

is the ratio, expressed as a percentage, of the 

dissolved oxygen concentration in the water to the 

dissolved oxygen concentration when at 

equilibrium with the atmosphere. 

juveniles utilizing habitat with HSI 

greater than zero has the potential to 

increase its biomass during the Juvenile 

Development season, thus contributing 

to successful propagation. Therefore, to 

derive protective dissolved oxygen 

criteria, the EPA evaluated seasonal 

percentiles of percent oxygen saturation 

to find the lowest value at which the 

QGAMs predict expected median HSI>0 

as the minimum thresholds for percent 

oxygen saturation that, if attained, 

would provide suitable habitat during 

that seasonal period. The EPA requests 

comment on the conclusion that HSI 

greater than zero defines suitable habitat 

for juvenile Atlantic Sturgeon growth 

and survival, or alternatively, if 

evidence could support that a value of 

HSI less than zero could also be 

protective or if a higher HSI threshold 

may be needed to protect propagation in 

the specified zones. Similarly, the EPA 

requests comment on its use of QGAM 

to relate percentiles of dissolved oxygen 

levels to the conditional median HSI. 

These models can be understood to find 

the minimum dissolved oxygen level 

that if achieved would result in an 

expectation that HSI would be equal to 

or greater than zero as often or more 

often than if it is less than zero. As an 

alternative, the QGAM could predict a 

lower conditional percentile, providing 

a high degree of certainty that HSI 

would be greater than zero if the 

dissolved oxygen level was attained. For 

example, at the dissolved oxygen level 

where the expected 25th percentile 

HSI=0, HSI would be expected to equal 

or exceed zero 75% of the time. 

The predicted HSI value relies on an 

expected distribution of percent oxygen 

saturation values during the season; 

therefore, the EPA selected two percent 

oxygen saturation percentiles as 

thresholds at or above which median 

HSI is expected to be greater than zero 

to maintain the expected distribution of 

percent oxygen saturation values. These 

two percentiles—the 10th percentile 

and the 50th percentile—describe the 

protective seasonal distribution of 

dissolved oxygen values. When both the 

10th percentile and 50th percentile are 

attained, they function together to 

ensure that a detrimental shift in the 

oxygen distribution (i.e., a shift causing 

more low oxygen levels) at either the 

low end (10th percentile) or the center 

(50th percentile) of the dissolved 

oxygen distribution has not occurred. 

Median HSI is expected to be zero or 

higher, allowing the annual cohort of 

juvenile Atlantic Sturgeon to maintain 

or increase its biomass, when the 10th 

percentile of oxygen saturation is at 

least 66% and the 50th percentile, or 

median, of oxygen saturation is at least 

74%. Therefore, the EPA expects oxygen 

levels will not impair juvenile Atlantic 

Sturgeon during the Juvenile 

Development season if the 10th 

percentile of oxygen saturation is at 

least 66% and the 50th percentile of 

oxygen saturation is at least 74%. 

Criteria Development for Spawning and 

Larval Development and Overwintering 

Seasons 

The Atlantic Sturgeon cohort model 

described above relies on experimental 

studies that were conducted using 

juvenile Atlantic Sturgeon and therefore 

provide information that is most 

relevant to juvenile growth and 

survival.62 Additionally, the underlying 

studies allocated most experimental 

treatments to water temperatures 

between 12 °C and 28 °C, with only a 

single experimental treatment at 6 °C 

and none at lower water temperatures.63

The EPA’s cohort modeling approach 

therefore does not apply to spawning 

and larval development lifestages and 

has minimal relevance to the 

overwintering period. Accordingly, the 

EPA did not use the cohort model to 

derive criteria for the Spawning and 

Larval Development or the 

Overwintering seasons. 

Instead, the EPA concluded that 

Atlantic Sturgeon larvae were likely to 

be as sensitive to low dissolved oxygen 

as juvenile Atlantic Sturgeon 64 and that 

overwintering juveniles have 

temperature-limited metabolism and 

therefore have similar or slightly lower 

oxygen requirements than juveniles in 

warmer waters (e.g., summer water 

temperatures).65 Thus, the EPA 

determined that the percent oxygen 

saturation threshold that would be 

protective of juveniles experiencing 

stressful (high) water temperatures 

during the Juvenile Development season 

would also be protective of larvae and 

overwintering juveniles not 

experiencing high water temperatures. 

Therefore, the EPA expects oxygen 

levels will not impair Atlantic Sturgeon 

when the 10th percentile of oxygen 

saturation is at least 66% during the 

Spawning and Larval Development and 

Overwintering seasons. The EPA notes 

that from 2002–2022, the median 

oxygen level during the Spawning and 

Larval Development and Overwintering 

seasons was well above levels expected 

to negatively impact either Atlantic 

Sturgeon or other oxygen-sensitive 

species. Therefore, the EPA concluded 

that a second criterion for a 50th 

percentile was not needed during these 

seasons. 

Criteria Expressed as Percent Oxygen 

Saturation 

Finally, the EPA derived the proposed 

criteria in terms of percent oxygen 

saturation, rather than in units of 

concentration (such as milligrams per 

liter or mg/L) for two main reasons.66

First, physiological effects of oxygen on 

aquatic organisms are directly related to 

percent oxygen saturation and indirectly 

related to dissolved oxygen 

concentration. As noted by Niklitschek 

and Secor (2009a), percent oxygen 

saturation or partial pressure are the 

most biologically relevant measures of 

oxygen because they determine the 

maximum rate at which aquatic 

organisms may obtain oxygen from the 

water. Second, percent oxygen 

saturation varies with water temperature 

less than dissolved oxygen 

concentration. Because oxygen 

solubility is higher in cold water than 

warm water, dissolved oxygen 

concentrations are often much higher in 

cold water. The strong negative 

relationship between dissolved oxygen 

concentration and temperature can 

complicate the interpretation of 

seasonal dissolved oxygen patterns. For 

example, in the Delaware River, 

dissolved oxygen concentrations 

increase quickly during fall as 

temperatures decrease, even though 

percent saturation increases more 

slowly. In this example, the increasing 

oxygen concentration gives the 

appearance that oxygen availability to 

aquatic organisms is increasing more 

rapidly than it is actually increasing. 

For Atlantic Sturgeon, this means that 

low levels of percent oxygen saturation 

may continue to impact growth and 

survival even though dissolved oxygen 

concentrations increase. Given this 

relationship between temperature and 

dissolved oxygen concentration, criteria 

expressed as concentration will be 

above or below the protective threshold 

at various times of the year as 


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67Stoklosa et al. (2018); Delaware River Basin 

Commission (2015). 

68The EPA selected a daily average duration 

because it is a readily measurable indicator of the 

oxygen levels at a daily timescale. The daily average 

is protective because variability of dissolved oxygen 

levels on a single day is small in the Delaware 

River. 

69More information is available in the associated 

document, Technical Support Document for the 

Proposed Rule: Water Quality Standards to Protect 

Aquatic Life in the Delaware River. 

temperature changes, whereas criteria 

expressed as percent oxygen saturation 

can be protective throughout the year. 

2. Proposed Dissolved Oxygen Criteria 

The EPA’s proposed dissolved oxygen 

criteria cover three distinct seasons 

based largely on Atlantic Sturgeon early 

life stages and are intended to protect all 

oxygen-sensitive species in the 

Delaware River, as explained above. The 

Spawning and Larval Development 

season occurs between March 1st and 

June 30th and captures a comprehensive 

range of resident aquatic species’ 

spawning periods.67 The Juvenile 

Development season occurs between 

July 1st and October 31st and captures 

critical early life stage growth and 

development for young-of-the-year 

Atlantic Sturgeon. The Overwintering 

season occurs between November 1st 

and February 28th (or 29th, in a leap 

year), when juvenile Atlantic Sturgeon 

growth is limited by low water 

temperatures. 

Each season has water quality criteria 

that each consist of three components: 

magnitude, duration, and exceedance 

frequency. The magnitude component 

indicates the required level of dissolved 

oxygen in the water, which in this 

proposal is presented in units of percent 

oxygen saturation. The duration 

component specifies the time period 

over which water quality is averaged 

before comparison with the criteria 

magnitude; in this proposal, the 

duration is a daily average.68 The 

exceedance frequency component 

specifies how often (e.g., percentage of 

the time) each criterion can be exceeded 

in each season while still ensuring that 

the use is protected. For this proposed 

rulemaking, the exceedance frequency is 

determined based on the dissolved 

oxygen percentile from which the 

magnitude is derived (i.e., the 10th 

percentile can be exceeded 10% of the 

time, which for a season consisting of 

123 days is 12 cumulative days of 

exceedance). For dissolved oxygen, an 

exceedance occurs when the oxygen 

level in the water is below the criterion 

value. 

In this proposed rulemaking, the 

Spawning and Larval Development and 

Overwintering seasons each have a 

single, identical dissolved oxygen 

criterion with a magnitude of 66% 

oxygen saturation, a daily average 

duration, and a 10% exceedance 

frequency (which allows for up to 12 

days of cumulative exceedance during 

each of these two seasons) (Table 6 of 

this preamble). The Juvenile 

Development season has two 

individually applicable dissolved 

oxygen criteria that together define a 

protective seasonal distribution of 

percent oxygen saturation. The criteria 

differ in both magnitude and 

exceedance frequency and both levels 

must be attained. The first Juvenile 

Development criterion defines the lower 

end of the distribution of oxygen levels 

and consists of a magnitude of 66% 

oxygen saturation, a daily average 

duration, and a 10% exceedance 

frequency (which allows for up to 12 

days cumulative exceedance during the 

season). The second Juvenile 

Development criterion defines the 

center of the distribution and consists of 

a magnitude of 74% oxygen saturation, 

a daily average duration, and a 50% 

exceedance frequency (which allows for 

up to 61 days cumulative exceedance 

during the season) (Table 6 of this 

preamble). 

TABLE 6—THE EPA’S PROPOSED DISSOLVED OXYGEN CRITERIA

Season 

Magnitude 

(percent 

oxygen 

saturation) 

Duration Exceedance frequency 

Spawning and Larval Development (March 1–June 

30).

66 Daily verage ................................... 10% (12 Days Cumulative). 

Juvenile Development (July 1–October 31) ............... 66 Daily Average ................................. 10% (12 Days Cumulative). 

74 Daily Average ................................. 50% (61 Days Cumulative). 

Overwintering (November 1–February 28/29) ............ 66 Daily Average ................................. 10% (12 Days Cumulative). 

3. Alternative Options Considered 

During the criteria derivation process, 

the EPA made several decisions based 

on the best available sound scientific 

information to ensure the dissolved 

oxygen criteria would be protective of 

the applicable and proposed aquatic life 

designated uses. In this section, the EPA 

presents three alternative options the 

Agency considered. For each 

alternative, the EPA examined 

information currently available at the 

time of this proposal. The EPA has 

concerns about whether each alternative 

would be protective of the aquatic life 

designated uses that include 

propagation; therefore, the EPA did not 

include any of these alternatives as part 

of its lead proposed criteria. However, 

the EPA requests comment and 

additional information on whether and 

how one or more of these alternatives 

could protect the applicable and 

proposed aquatic life designated uses in 

the specified zones of the Delaware 

River and if so, what anticipated 

benefits would be associated with the 

alternative compared to the EPA’s 

proposed criteria.69

Alternative 1: Dissolved Oxygen 

Criteria Expressed as Concentration 

(mg/L). 

The EPA’s proposed dissolved oxygen 

criteria are expressed as percent oxygen 

saturation, as described in section 

IV.C.1 of this preamble. However, the 

EPA recognizes that some stakeholders 

might be more familiar with dissolved 

oxygen criteria expressed as 

concentration or might have other 

reasons for preferring criteria expressed 

as concentration. The EPA is seeking 

comment on whether dissolved oxygen 

criteria expressed as concentration 

(mg/L) would be protective of oxygensensitive species during each season. 

To calculate Juvenile Development 

season criteria expressed as 

concentration (mg/L), the EPA followed 

an analogous approach to the method 

used for determining criteria as percent 

oxygen saturation, as explained in 

section IV.C.1 of this preamble. The 

EPA used quantile generalized additive 

models relating seasonal percentiles of 

dissolved oxygen concentration to the 

expected median habitat suitability 

index (HSI). The EPA selected as the 

alternative criteria values the dissolved 


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70The EPA assumed salinity = 0 for each 

conversion from percent oxygen saturation to 

concentration in the Spawning and Larval 

Development and Overwintering seasons. 

71Seasonal 90th percentile and mean water 

temperature were calculated using the daily 

climatology computed for Chester for March 1, 

2012–June 30th, 2022, for the Spawning and Larval 

Development season and November 1, 2011– 

February 28, 2022, for the Overwintering season. 

72United States Environmental Protection 

Agency. (2000). Ambient Aquatic Life Water 

Quality Criteria for Dissolved Oxygen (Saltwater): 

Cape Cod to Cape Hatteras. Document ID: EPA– 

822–R–00–012. November 2000. https:// 

www.epa.gov/sites/default/files/2018-10/ 

documents/ambient-al-wqc-dissolved-oxygen-capecode.pdf; Batiuk, R.A., Breitburg, D.L., Diaz, R.J., 

Cronin, T.M., Secor, D.H., and Thursby, G. (2009). 

Derivation of habitat-specific dissolved oxygen 

criteria for Chesapeake Bay and its tidal tributaries. 

Journal of Experimental Marine Biology and 

Ecology 381: S204–S215. https://doi.org/10.1016/

j.jembe.2009.07.023. 

73More information on dissolved oxygen trends 

in the specified zones of the Delaware River is 

available in the associated rule documents, 

Technical Support Document for the Proposed 

Rule: Water Quality Standards to Protect Aquatic 

Life in the Delaware River and Economic Analysis 

for the Proposed Rule: Water Quality Standards to 

Protect Aquatic Life in the Delaware River. 

oxygen concentration for which the 

expected median HSI is zero (Table 7 of 

this preamble). 

To calculate dissolved oxygen criteria 

expressed as concentration for the 

Spawning and Larval Development and 

Overwintering seasons, the EPA started 

with the criteria computed as percent 

oxygen saturation (Table 6 of this 

preamble) and converted each of these 

to a concentration using each of the 

following two approaches, which 

differed based on water temperature 

assumptions.70 The EPA’s first approach 

uses the 90th percentile of water 

temperatures in each season, whereas 

the second approach uses the average 

water temperature in each season.71 The 

90th percentile approximates the 

highest water temperature in each 

season, which corresponds to when 

dissolved oxygen levels are generally at 

their lowest and therefore impacts to 

aquatic life are most likely to occur. In 

the Delaware River, the highest 

temperatures in the Spawning and 

Larval Development season occur in late 

June and the highest temperatures in the 

Overwintering season occur in early 

November. On the other hand, the EPA’s 

second approach using an average water 

temperature results in the concentration 

that minimizes the magnitude of 

deviations in either direction from the 

protective level across the season. 

Because the average water temperature 

is lower than the 90th percentile water 

temperature, the EPA’s second approach 

resulted in higher dissolved oxygen 

concentrations than the first approach 

(Table 7 of this preamble). 

In table 7 below, the EPA leads with 

alternative criteria based on the 90th 

percentile water temperatures because 

existing dissolved oxygen criteria 

guidance and criteria derivation efforts 

in other states have commonly focused 

on the warmest conditions that occur, 

which are the most critical for 

mitigating impacts to aquatic life due to 

low oxygen.72 For consideration, the 

EPA presents alternative criteria based 

on average water temperatures in 

parentheses. 

TABLE 7—ALTERNATIVE 1: DISSOLVED OXYGEN CRITERIA EXPRESSED AS CONCENTRATION

[mg/L] 

Season 

Water temperature 

(°C) 

Magnitude 

(mg/L) Duration Exceedance frequency 

Spawning and Larval Development (March 

1–June 30).

* 23.3 (14.7) * 5.6 (6.7) Daily Average ........................ 10% (12 Days Cumulative). 

Juvenile Development (July 1–October 31) ... + N/A 5.4 Daily Average ........................ 10% (12 Days Cumulative). 

N/A+ ................................................................ 6.1 Daily Average 50% (61 Days Cumulative).

Overwintering (November 1–February 28/29) * 12.4 (5.6) * 7.0 (8.3) Daily Average ........................ 10% (12 Days Cumulative). 

* The 90th percentile of seasonal water temperature and corresponding criterion is used for the main estimate, while the average water temperature and corresponding criterion is shown in parentheses. +Water temperature is not applicable during the Juvenile Development season because the criteria magnitudes are derived from the EPA’s Atlantic Sturgeon cohort model, described in section IV.C.1 of this preamble. 

Concentration-based criteria derived 

using the EPA’s first approach (based on 

the 90th percentile water temperatures) 

would be equivalent to the EPA’s 

proposed 66% oxygen saturation when 

water temperature is near the 90th 

percentile temperature and oxygen is 

near the lowest point in each season. 

However, during periods in each season 

when water temperature is lower than 

the 90th percentile temperature, the 

concentration-based criteria would be 

below the level that is equivalent to the 

EPA’s proposed 66% oxygen saturation 

level. For example, when water 

temperature is 2 °C in mid-winter, 

oxygen saturation is 66% when the 

dissolved oxygen concentration is 9.1 

mg/L. The EPA therefore has concerns 

about whether dissolved oxygen criteria 

expressed as concentration for this 

alternative would be protective for the 

Spawning and Larval Development and 

Overwintering seasons. Similar to the 

first approach, the concentration 

derived using the EPA’s second 

approach (average water temperature) is 

also below the level that is equivalent to 

66% oxygen saturation when water 

temperature is below the seasonal 

average. During periods in each season 

when the water temperature is warmer 

than the average, concentrations 

calculated using the EPA’s second 

approach would result in an oxygen 

saturation higher than 66%.73

The EPA provided the concentrations 

in table 7 of this preamble that result 

from the methods described above to 

help facilitate public comment. The 

EPA also requests public input and 

supporting information about other 

ways the Agency could develop 

dissolved oxygen criteria expressed as 

concentration—particularly for the 

Spawning and Larval Development and 

Overwintering seasons—to protect the 

relevant aquatic life uses in accordance 

with the CWA. 

Alternative 2: Single Dissolved 

Oxygen Criterion During the Juvenile 

Development Season with a 10% 

Exceedance Frequency. 

The EPA’s proposed dissolved oxygen 

criteria for the critical Juvenile 

Development season consist of two 

values—one that may be exceeded 10% 

of the time and one that may be 

exceeded 50% of the time—that must 

both be met during the season, as 

explained in section IV.C.1 of this 

preamble. However, the EPA recognizes 

that some stakeholders might prefer the 

simpler criteria framework a single 

criterion would afford or may have 

other reasons for preferring a single 

value. 


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74Stephen, C.E., Mount, D.I., Hansen, D.J., 

Gentile, J.R., Chapman, G.A., and Brungs, W.A. 

(1985). Guidelines for Deriving Numerical National 

Water Quality Criteria for the Protection of Aquatic 

Organisms and Their Uses. United States 

Environmental Protection Agency. Document ID: 

PB85–227049. https://www.epa.gov/sites/default/ 

files/2016-02/documents/guidelines-water-qualitycriteria.pdf; United States Environmental Protection 

Agency. (2023). Proceedings from the EPA 

Frequency and Duration Experts Workshop: 

September 11–12, 2019. Document ID: EPA–820–R– 

23–002. February 2023. https://www.epa.gov/ 

system/files/documents/2023-02/proceedingsfrequency-duration-workshop.pdf. 

The EPA is seeking comment and 

supporting information on applying a 

single dissolved oxygen criterion with a 

10% exceedance frequency during the 

Juvenile Development season, including 

whether criteria expressed with a single 

criterion would protect the applicable 

and proposed aquatic life designated 

uses. This could mean applying a single 

criterion of 66% oxygen saturation (or 

5.4 mg/L, if expressed as concentration) 

with a 10% exceedance frequency for 

the Juvenile Development season. The 

Overwintering and Spawning and Larval 

Development seasons are unaffected by 

this alternative. 

The EPA also requests public input 

and supporting information about other 

potential options the Agency could 

consider for dissolved oxygen criteria in 

the form of a single criterion to protect 

the aquatic life uses in accordance with 

the CWA. 

Alternative 3: Inclusion of a 1-in-3- 

Year Interannual Exceedance 

Frequency. 

The EPA’s proposed criteria do not 

include an interannual exceedance 

frequency and therefore would need to 

be met every year. However, the EPA 

recognizes that some stakeholders might 

prefer criteria with an interannual 

exceedance frequency to help 

accommodate the impact of 

environmental variability on dissolved 

oxygen conditions in the specified 

zones of the Delaware River. The EPA 

is seeking comment and supporting 

information on the addition of a 1-in-3- 

year interannual exceedance frequency 

as part of the dissolved oxygen criteria. 

The EPA is particularly interested in 

how and why this approach would 

protect the applicable and current 

aquatic life uses. 

If a 1-in-3-year interannual 

exceedance frequency were included as 

part of the dissolved oxygen criteria, it 

would mean that in any three-year 

period, all criteria would need to be 

attained in at least two years. An 

exceedance would occur in any year 

where one or more of the criteria were 

not attained. The following two 

examples describe how a 1-in-3-year 

interannual exceedance frequency could 

function. 

Example 1: If, in a given year, the 

dissolved oxygen during the Juvenile 

Development season fell below 66% 

saturation more than 10% of the time, 

then that year would not meet the 

Juvenile Development 10th percentile 

criterion. Therefore, that year would 

count as one year of exceedance towards 

the 1-in-3-year interannual exceedance 

frequency. If another criterion, for 

example the Spawning and Larval 

Development criterion, was not met in 

that same year, then it would still only 

count as one year of exceedance despite 

the fact that two criteria were not met 

that year (Table 8 of this preamble). 

TABLE 8—EXAMPLE 1 SCENARIO WHERE DISSOLVED OXYGEN CRITERIA WITH THE 1-IN-3-YEAR INTERANNUAL

EXCEEDANCE FREQUENCY ARE MET

Season 

Was the seasonal criterion met? 

Year 1 Year 2 Year 3 

Spawning and Larval Development ...................................................... No ............................... Yes ............................. Yes. 

Juvenile Development—10th Percentile ............................................... No ............................... Yes ............................. Yes. 

Juvenile Development—50th Percentile ............................................... Yes ............................. Yes ............................. Yes. 

Overwintering ........................................................................................ Yes ............................. Yes ............................. Yes. 

Does the Full Year Meet Criteria? ........................................................ No ............................... Yes ............................. Yes. 

Example 2: If, in a given year, the 

dissolved oxygen during the Juvenile 

Development season fell below 66% 

saturation more than 10% of the time, 

then that year would not meet the 

Juvenile Development 10th percentile 

criterion. If the following year, the 

Juvenile Development season fell below 

74% saturation more than 50% of the 

time, then that year would not meet the 

Juvenile Development 50th percentile 

criterion (Table 9 of this preamble). In 

this scenario, the first and second year 

in the three-year period both did not 

meet the criteria; therefore, the 

interannual exceedance frequency was 

not met. 

TABLE 9—EXAMPLE 2 SCENARIO WHERE DISSOLVED OXYGEN CRITERIA WITH THE 1-IN-3-YEAR INTERANNUAL

EXCEEDANCE FREQUENCY ARE NOT MET

Season 

Was the seasonal criterion met? 

Year 1 Year 2 Year 3 

Spawning and Larval Development ...................................................... Yes ............................. Yes ............................. Yes. 

Juvenile Development—10th Percentile ............................................... No ............................... Yes ............................. Yes. 

Juvenile Development—50th Percentile ............................................... Yes ............................. No ............................... Yes. 

Overwintering ........................................................................................ Yes ............................. Yes ............................. Yes. 

Does the Full Year Meet Criteria? ........................................................ No ............................... No ............................... Yes. 

The EPA has historically considered it 

appropriate to apply a 1-in-3-year 

exceedance frequency in the context of 

aquatic life criteria for toxic pollutants, 

based on the ability of aquatic 

ecosystems to recover from criteria 

exceedances and natural variations in 

flow and the concentrations of the 

pollutant in a waterbody.74 However, the EPA does not typically apply this 

construct to criteria for conventional 

water quality parameters like dissolved 


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88328 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

75United States Environmental Protection 

Agency. (2000). Ambient Aquatic Life Water 

Quality Criteria for Dissolved Oxygen (Saltwater): 

Cape Cod to Cape Hatteras. Document ID: EPA– 

822–R–00–012. November 2000. https:// 

www.epa.gov/sites/default/files/2018-10/ 

documents/ambient-al-wqc-dissolved-oxygen-capecode.pdf. 

76 In the December 1, 2022, Administrator’s 

Determination, the EPA determined that revised 

dissolved oxygen criteria are necessary to protect a 

propagation designated use. This proposed 

rulemaking includes dissolved oxygen criteria that 

are protective of all life stages of resident and 

migratory aquatic life species in the Delaware River 

(section IV.C. of this preamble). 

oxygen due to inherent differences 

between these parameters and toxic 

pollutants. For example, dissolved 

oxygen is typically not directly 

regulated in the same manner as toxic 

pollutants because low dissolved 

oxygen conditions (such as hypoxia) are 

a symptom of a related issue, such as 

nutrient or ammonia pollution.75 The 

EPA also requests public input and 

supporting information regarding any 

scientific approaches that can be used to 

predict the impact of periodic low 

oxygen levels on populations of aquatic 

organisms. 

V. Endangered Species Act 

Consultation 

Section 7(a)(2) of the Endangered 

Species Act (ESA) requires that each 

Federal Agency ensure that any action 

authorized, funded, or carried out by 

such Agency is not likely to jeopardize 

the continued existence of any 

endangered or threatened species or 

result in the destruction or adverse 

modification of critical habitat. Pursuant 

to section 7(a)(2) of the ESA, the EPA 

will consult with NOAA Fisheries 

concerning this rulemaking action 

proposing a designated aquatic life use 

including propagation and associated 

dissolved oxygen criteria in the 

specified zones of the Delaware River. 

The EPA will work closely with NOAA 

Fisheries to ensure that any WQS the 

Agency finalizes are not likely to 

jeopardize the continued existence of 

any endangered or threatened species or 

result in the destruction or adverse 

modification of designated critical 

habitat in the specified zones of the 

Delaware River. As a result of this 

consultation, the EPA may modify some 

provisions of this proposed rule. 

VI. Applicability 

The EPA is proposing a Federal 

designated use that would apply in New 

Jersey and Pennsylvania, in addition to 

those states’ designated uses that are 

already applicable. This means that for 

the specified zones of the Delaware 

River, the EPA is proposing to 

supplement, rather than replace, New 

Jersey’s and Pennsylvania’s currently 

applicable aquatic life designated uses. 

Therefore, New Jersey’s and 

Pennsylvania’s currently applicable 

aquatic life designated uses would 

remain applicable for CWA purposes. 

Those states’ current water quality 

criteria associated with those uses 

would also remain applicable for CWA 

purposes, with the exception of any 

aquatic life criteria for dissolved 

oxygen, which would be replaced by the 

criteria that the EPA promulgates 

through this rulemaking, if finalized.76

The EPA concluded that this approach 

was the best way to make clear which 

of the states’ WQS would and would not 

be revised by this rulemaking, if 

finalized. The EPA requests comment 

on this approach. 

In addition, the EPA is proposing 

dissolved oxygen criteria that would 

replace Delaware’s, New Jersey’s, and 

Pennsylvania’s existing dissolved 

oxygen criteria for the specified zones of 

the Delaware River. The EPA notes that 

there are aquatic life criteria for 

pollutants and parameters other than 

dissolved oxygen that are in effect for 

CWA purposes—not only in the zones 

covered by this proposed rulemaking, 

but also for other zones of the Delaware 

River that already include aquatic life 

propagation as a designated use; those 

criteria are not impacted by this 

rulemaking. 

Since the EPA is only proposing to 

promulgate revised dissolved oxygen 

criteria for the specified zones of the 

Delaware River, Delaware, New Jersey, 

and Pennsylvania should evaluate 

whether other aquatic life criteria 

should similarly be added or revised for 

the specified zones or other zones of the 

Delaware River. One way these states 

can review their WQS is through the 

triennial review process. As explained 

in section III of this preamble, states 

must review their WQS at least once 

every three years and, if appropriate, 

revise standards or adopt new standards 

(40 CFR 131.20(a)). The EPA 

recommends that Delaware, New Jersey, 

and Pennsylvania review their existing 

aquatic life criteria during their next 

triennial review to determine if new or 

revised aquatic life criteria would be 

appropriate to protect all applicable 

aquatic life designated uses, including 

any Federal designated use that the EPA 

may promulgate as part of a final rule. 

VII. Conditions Where Federal Water 

Quality Standards Would Not Be 

Promulgated or Would Be Withdrawn 

As noted, under the CWA, states and 

authorized tribes have the primary 

responsibility for developing and 

adopting WQS for their navigable waters 

(CWA section 303(a) through (c)). 

Although the EPA is proposing a revised 

aquatic life designated use and 

protective dissolved oxygen criteria for 

the specified zones of the Delaware 

River, each state retains the option to 

adopt and submit to the EPA for review 

its own revised designated use and 

dissolved oxygen criteria that are 

consistent with CWA section 303(c) and 

the EPA’s implementing regulation to 

address the EPA’s Administrator’s 

Determination. 

A. Conditions Where Federal Standards 

Would Not Be Promulgated 

If Delaware, New Jersey, and 

Pennsylvania adopt and submit revised 

WQS that addresses the EPA’s 

December 1, 2022, Administrator’s 

Determination, and the EPA approves 

those WQS before finalizing this 

proposed rulemaking, then a Federal 

promulgation would no longer be 

required under the CWA. Similarly, if 

one state adopts and submits WQS 

consistent with this proposed 

rulemaking, and the EPA approves those 

WQS before finalizing this proposed 

rulemaking, then a Federal 

promulgation would no longer be 

required under the CWA for that state. 

B. Conditions Where Federal Standards 

Would Be Withdrawn 

If the EPA finalizes this proposed 

rulemaking and Delaware, New Jersey, 

and Pennsylvania subsequently adopt 

and submit revised WQS to the EPA, 

and the EPA approves those WQS, then 

the EPA would undertake a rulemaking 

to withdraw the federally promulgated 

use and/or dissolved oxygen criteria (40 

CFR 131.21(c)). Similarly, if one state 

adopts and submits revised WQS to the 

EPA, and the EPA approves those WQS, 

then the EPA would undertake a 

rulemaking to withdraw the federally 

promulgated WQS for that state. 

If Delaware’s, New Jersey’s, and/or 

Pennsylvania’s adopted dissolved 

oxygen criteria are as stringent or more 

stringent than the federally promulgated 

criteria, then that state’s criteria would 

immediately become the CWAapplicable criteria upon the EPA’s 

approval. If Delaware’s, New Jersey’s, 

and/or Pennsylvania’s adopted 

dissolved oxygen criteria are less 

stringent than the federally promulgated 

criteria, and the EPA approves those 

less stringent criteria, then those EPAapproved criteria would become the 

applicable criteria for CWA purposes 

only after the EPA withdraws its 

federally promulgated criteria for the 

relevant state(s). 


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77The EPA’s Integrated Reporting Guidance is 

available at: https://www.epa.gov/tmdl/integratedreporting-guidance-under-cwa-sections-303d-305band-314. 

78 Delaware River Basin Commission (2022a, 

2022b). 

79More details are available in the document, 

Economic Analysis for the Proposed Rule: Water 

Quality Standards to Protect Aquatic Life in the 

Delaware River. 

VIII. Alternative Regulatory 

Approaches and Implementation 

Mechanisms 

The Federal WQS regulations at 40 

CFR part 131 provide several 

approaches that Delaware, New Jersey, 

and Pennsylvania could use at each 

state’s discretion when implementing or 

deciding how to implement the 

federally promulgated dissolved oxygen 

criteria, if finalized. The EPA has 

identified two approaches—WQS 

Variances and NPDES Permit 

Compliance Schedules—that might be 

of particular interest for the states 

covered by this proposed rulemaking. 

Additionally, the EPA included a 

discussion about CWA section 303(d)/ 

305(b) water quality assessments to 

clarify potential options that may be 

available to states in the specific 

circumstances relevant to this 

rulemaking. 

A. Water Quality Standards Variances 

A WQS variance is a time-limited 

designated use and criterion, for a 

specific pollutant or water quality 

parameter, that reflects the highest 

attainable condition (HAC) during the 

term of the WQS variance (40 CFR 

131.3(o)). WQS variances can be used to 

incrementally improve water quality 

where the designated use and criterion 

are unattainable for a period of time. 

The state would need to demonstrate 

that attaining the applicable designated 

use and dissolved oxygen criterion 

would not be feasible for a period of 

time (i.e., during the term of the WQS 

variance) because of one of the factors 

specified in 40 CFR 131.14(b)(2)(i)(A) 

and specify the actions that will be 

taken to make incremental water quality 

improvements during the term of the 

WQS variance. 

If Delaware, New Jersey, and/or 

Pennsylvania choose/s to adopt a WQS 

variance, the state/s must specify in the 

WQS variance the term and the interim 

requirements of the WQS variance. The 

term must be justified by describing the 

pollutant control activities expected to 

occur over that term to achieve the 

HAC. The interim requirements must be 

a quantitative expression that reflects 

the HAC using one of the options 

provided at 40 CFR 131.14(b)(1)(ii). 

WQS variances adopted in accordance 

with 40 CFR 131.14 and approved by 

the EPA for CWA purposes provide a 

legal avenue for states to write NPDES 

permit limits that are based on the HAC 

during the term of the WQS variance, 

while simultaneously implementing 

controls to make incremental water 

quality improvements toward ultimately 

attaining the applicable designated use 

and dissolved oxygen criterion. 

B. NPDES Permit Compliance Schedules 

The EPA’s regulations at 40 CFR 

122.47 and 131.15 address how 

permitting authorities can use schedules 

for compliance with a water-qualitybased effluent limitation (WQBEL) in an 

NPDES permit, if the discharger needs 

time to undertake an enforceable 

sequence of actions—such as facility 

upgrades or operation changes—leading 

to compliance with the WQBEL. The 

EPA’s regulation at 40 CFR 122.47 

allows states authorized to administer 

the NPDES program to include 

compliance schedules in NPDES 

permits, when appropriate and where 

authorized by the state’s WQS, provided 

the compliance schedule authorizing 

provision was approved by the EPA. 

Such compliance schedules may be 

used to implement any CWA-effective 

WQS, including any WQS that the EPA 

promulgates as part of a final rule. 

C. Clean Water Act Section 303(d)/ 

305(b) Water Quality Assessments 

If the EPA promulgates revised 

aquatic life WQS for the specified zones 

of the Delaware River and they become 

effective for CWA purposes, Delaware, 

New Jersey, and Pennsylvania will have 

an obligation under CWA sections 

303(d) and 305(b) to assess whether the 

WQS are being attained. The EPA 

anticipates there may be a period of 

time immediately after promulgation of 

the revised WQS when the WQS will 

not be attained because the actions and 

procedures required to achieve 

compliance will take time to implement. 

In this scenario, any of the relevant 

zones not attaining the WQS should be 

classified as impaired on the relevant 

303(d)/305(b) Integrated Report(s) (IR) 

that is submitted to the EPA for review. 

Per the CWA and the EPA’s 

implementing regulations, waters that 

are assessed as impaired by a pollutant 

typically require the development of a 

Total Maximum Daily Load (TMDL), 

which is a regulatory planning tool 

designed to restore water quality via 

allocations of pollutant reductions to 

relevant point and non-point sources. 

The EPA regulations also recognize that 

other pollution control requirements 

may obviate the need for a TMDL. 

Specifically, impaired waters do not 

require a TMDL if: (1) technology-based 

effluent limitations required by the 

CWA; (2) more stringent effluent 

limitations required by a state, local, or 

Federal authority; or (3) other pollution 

control requirements (e.g., best 

management practices) required by a 

state, local, or Federal authority are 

stringent enough to implement 

applicable WQS (40 CFR 130.7(b)(1)). 

Impaired waters that do not require a 

TMDL because they satisfy one of these 

alternatives are commonly referred to as 

Category 4b waters, as described in the 

EPA’s Integrated Reporting Guidance for 

CWA sections 303(d), 305(b), and 314.77

DRBC developed a model to evaluate 

sources of pollution that affect dissolved 

oxygen levels in the specified zones of 

the Delaware River and concluded that 

point sources are the primary 

contributor to oxygen depletion within 

those zones.78 DRBC therefore 

concluded that further controls on point 

sources are needed to achieve dissolved 

oxygen water quality conditions that 

support aquatic life designated uses that 

include propagation in the specified 

zones. The EPA’s economic analysis 

evaluates point source controls that are 

expected to result in dissolved oxygen 

levels that meet EPA’s proposed 

criteria.79 If, after finalization of this 

rulemaking, DRBC, Delaware, New 

Jersey, or Pennsylvania require effluent 

limitations and/or other pollution 

control requirements that the EPA 

agrees are stringent enough to 

implement the final dissolved oxygen 

criteria, the specified zones may be a 

candidate for Category 4b in future IRs. 

The EPA will work with Delaware, New 

Jersey, and Pennsylvania, in 

consultation with DRBC, on future IRs 

to determine the appropriate assessment 

status for the waters that are subject to 

this rulemaking. 

IX. Economic Analysis 

The EPA conducted an economic 

analysis to evaluate the potential costs 

and benefits associated with this 

proposed rulemaking. In the high-level 

summary of the EPA’s economic 

analysis below, the EPA first describes 

a baseline scenario that is intended to 

characterize the world in the absence of 

the EPA’s proposed rule. Next, the EPA 

describes development of a policy 

scenario based on potential pollution 

control actions that, if implemented, can 

be expected to meet the EPA’s proposed 

dissolved oxygen criteria. Finally, the 

EPA evaluates the anticipated costs and 

benefits associated with the policy 

scenario and the EPA’s proposed 

criteria. More details and information 


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88330 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

80While the EPA normally assumes full 

compliance with existing LTCPs, for this proposed 

rulemaking, the EPA is also assuming full 

compliance with planned LTCPs. Because planned 

LTCPs are not final and therefore are subject to 

change, this adds uncertainty to the baseline 

conditions. 

81 Delaware River Basin Commission (2022a); 

DELCORA. (2023). Combined Sewer System: 

DELCORA CSO LTCP. https://www.delcora.org/ 

combined-sewer-systems/delcora-cso-ltcp/; 

Philadelphia Water Department. (2023). CSO Long 

Term Control Plan. https://water.phila.gov/ 

reporting/ltcp/; State of New Jersey Division of 

Water Quality. (2023). Long Term Control Plan 

Submittals. https://www.nj.gov/dep/dwq/csoltcpsubmittals.htm. 

82The EPA determined that the model runs from 

DRBC were sufficient for use in this economic 

analysis. 

83 Delaware River Basin Commission (2022a). 

84 Id.; Kleinfelder Inc. (2021). Nitrogen Reduction 

Cost Estimation Study Final Summary Report. 

https://www.nj.gov/drbc/library/documents/

NitrogenReductionCostEstimates_

KleinfelderJan2021.pdf; Kleinfelder Inc. (2023). 

Delaware River Basin Commission Nitrogen 

Reduction Cost Estimation Study—Supplemental 

Cost Addendum 2 Technical Memorandum—Final. 

https://www.nj.gov/drbc/library/documents/

NitrogenReductionCostEstimates_Kleinfelder_

aug2023addendum.pdf. 

are available in the associated 

document, Economic Analysis for the 

Proposed Rule: Water Quality Standards 

to Protect Aquatic Life in the Delaware 

River. 

A. Baseline for the Analysis 

The baseline is intended to 

characterize the world in the absence of 

the EPA’s proposed rule. The EPA 

typically assumes full compliance with 

existing regulations and requirements— 

including CSO long-term control plans 

(LTCPs)—even if they are not yet fully 

implemented, as a basis for estimating 

the cost and benefits of proposed 

regulations. This baseline approach 

ensures that the cost and benefits of the 

existing regulations and requirements 

are not double counted. 

In this economic analysis, the EPA 

assumes that without the proposed rule, 

the less stringent WQS (that do not 

support aquatic life propagation) 

currently in effect for CWA purposes 

would remain in effect (section III.D. of 

this preamble). Accordingly, the EPA 

assumes that water quality conditions in 

the specified zones of the Delaware 

River, particularly during the Juvenile 

Development season (July 1–October 

31), would continue to experience low 

oxygen levels that do not support 

aquatic life propagation, even with 

implementation of existing and planned 

CSO LTCPs.80 Along the specified zones 

of the Delaware River, there are three 

combined sewer systems with CSO 

LTCPs that are relevant for 

consideration by the EPA as part of the 

baseline. The Philadelphia Water 

Department, Camden County Municipal 

Utilities Authority, and Delaware 

County Regional Water Quality Control 

Authority all have LTCPs that are either 

approved or in progress.81 The EPA 

expects implementation of these LTCPs, 

when finalized, to occur regardless of 

the EPA’s proposed rule. Therefore, the 

EPA included estimated CSO volume 

reductions for these three dischargers as 

part of the baseline for this economic 

analysis. 

DRBC modeled the effect of pollution 

reduction on dissolved oxygen levels in 

the Delaware River and provided the 

EPA with water quality simulation 

results under both baseline and 

‘‘restored’’ conditions for the years 

2012, 2018, and 2019.82 Baseline 

simulations predict water quality 

conditions associated with the discharge 

of actual wastewater treatment plant 

(WWTP) flows at existing levels of 

treatment and after full implementation 

of LTCPs. The restored simulations 

predict water quality conditions 

associated with the discharge of actual 

WWTP flows at treatment levels that 

include additional effluent treatment 

and after full implementation of LTCPs. 

Of the three available years (2012, 

2018, and 2019), the EPA selected the 

2019 year as representative of the most 

typical conditions in the relevant zones 

of the Delaware River. In comparison, 

2012 had atypically poor conditions 

(low percent oxygen saturation, high 

water temperature), while 2018 had 

atypically good conditions (high percent 

oxygen saturation, low water 

temperature). Therefore, model runs 

used in this economic analysis are based 

on 2019 conditions. 

B. Development of the Policy Scenario 

There is a wide range of potential 

paths that Delaware, New Jersey, and 

Pennsylvania may choose to take when 

implementing the EPA’s proposed WQS. 

For this economic analysis, the EPA 

relied on available data to develop a 

policy scenario based on modeled 

pollution controls developed by DRBC 

that the EPA expects would meet the 

Agency’s proposed dissolved oxygen 

criteria. Actual benefits, costs, and 

impacts will depend on the choices that 

states would make in implementing the 

proposed WQS, which may differ from 

the policy scenario in this economic 

analysis. 

The EPA’s proposed dissolved oxygen 

criteria apply to three seasons (section 

IV.C. of this preamble). Therefore, when 

developing a policy scenario for this 

proposed rulemaking, the EPA 

evaluated potential pollution control 

actions that would be expected to meet 

the EPA’s criteria in each of the three 

seasons. The EPA began by evaluating 

water quality monitoring data for the 

past decade from two continuous 

monitoring stations in the relevant 

zones of the Delaware River—Penn’s 

Landing in Zone 3 and Chester in Zone 

4. Based on the monitoring data, the 

EPA expects that the Agency’s proposed 

dissolved oxygen criteria for the 

Spawning and Larval Development and 

Overwintering seasons will likely be met 

without the need for additional WWTP 

upgrades or other controls beyond the 

baseline conditions (i.e., the LTCPs). 

Monitoring data for the Juvenile 

Development season indicated that 

additional pollution control actions are 

likely necessary to meet the EPA’s 

proposed criteria in that season. To 

develop a policy scenario for the 

Juvenile Development season, the EPA 

relied on modeled data from DRBC 

predicting oxygen levels in 2019 in the 

specified zones of the Delaware River 

following a set of WWTP pollution 

control actions for certain dischargers. 

Modeled data for restored conditions are 

described in the baseline section above, 

while WWTP controls are described in 

the cost section below. The EPA expects 

that this policy scenario (hereafter, the 

‘‘2019 restored scenario’’) will meet the 

proposed criteria during the Juvenile 

Development season. 

C. Potential Costs 

The EPA estimated compliance costs 

for the proposed WQS based on 

estimates for WWTPs to reduce effluent 

ammonia nitrogen concentrations and 

raise effluent dissolved oxygen 

concentrations. Although there are 

several causes that contribute to low 

dissolved oxygen conditions in the 

specified zones of the Delaware River, 

DRBC identified ammonia nitrogen 

loadings from WWTPs as the leading 

cause of oxygen-depletion in the river.83

As a result, for the purpose of this 

economic analysis, the EPA assumed 

that additional pollution control 

technologies implemented at WWTPs is 

the most likely way that Delaware, New 

Jersey, and Pennsylvania will 

implement the proposed WQS. 

Therefore, the EPA evaluated WWTP 

controls rather than other non-point 

source controls for this cost analysis. 

The EPA relied on cost information 

from several DRBC studies to estimate 

the costs of achieving the proposed 

WQS.84 DRBC’s 2022 Analysis of 

Attainability report categorized WWTPs 

as either class A′, A, or B facilities. 

DRBC determined that discharges from 

Class A′, A, and B facilities have a major 


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85 Delaware River Basin Commission (2022a). 

86The EPA has used this benefit transfer 

approach on numerous occasions, most recently in 

the Benefit and Cost Analysis for Proposed 

Revisions to the Effluent Limitations Guidelines and 

Standards for the Steam Electric Power Generating 

Point Source Category, which is available at https:// 

www.epa.gov/system/files/documents/2023-03/ 

steam-electric-benefit-cost-analysis_proposed_feb2023.pdf. 

impact, a marginal impact, or no 

measurable impact on oxygen levels in 

the specified zones, respectively. The 

EPA’s 2019 restored scenario follows 

DRBC’s approach by including the 

seven Class A′ and two Class A facilities 

and excluded the three Class B 

facilities.85

The EPA used WWTP-specific 

(capital, operations and maintenance 

(O&M)) compliance costs from 

Kleinfelder Inc. (2021, 2023) to estimate 

compliance costs, based on the 

discharger classification. Total 

compliance costs include the costs 

associated with both of the following: 

1. Class A′ Facilities: Costs associated 

with reductions in effluent ammonia 

nitrogen concentrations to 1.5 mg/L 

from May 1 through October 31 and 

increases in effluent oxygen 

concentrations to a monthly average of 

6 mg/L year-round for the seven 

WWTPs categorized as Class A′ 

facilities. 

2. Class A Facilities: Costs associated 

with reductions in effluent ammonia 

nitrogen concentrations to 5 mg/L from 

May 1 through October 31 for the two 

WWTPs categorized as Class A facilities. 

To estimate annualized compliance 

costs, the EPA assumed capital costs 

occur upfront in 2024 followed by a 5- 

year construction period. Consistent 

with Kleinfelder Inc. (2021, 2023), the 

EPA assumed O&M costs occur over a 

25-year period from 2029 through 2053. 

The EPA thus annualized costs over a 

30-year analysis period between 2024 

and 2053 and discounted all cost values 

to 2024, using a 3 percent discount rate. 

Table 10 of this preamble presents the 

annualized compliance costs associated 

with achieving the EPA’s proposed 

WQS, using a 3 percent discount rate. 

The estimated total annualized 

compliance cost across nine WWTPs is 

$137.1 million (2022$). These costs vary 

considerably between the nine WWTPs, 

ranging from $1.9 million at the Lower 

Bucks County Joint Municipal Authority 

WWTP to $37.6 million at the 

Philadelphia Water Department (PWD) 

Southwest Water Pollution Control 

Plant (2022$). Among the dischargers, 

PWD bears the highest proportion of 

total costs, with its three facilities’ 

combined costs accounting for over 50 

percent of total costs. Overall, 66 

percent of the costs are attributable to 

capital and 34 percent are attributable to 

O&M. 

TABLE 10—ANNUALIZED COMPLIANCE COSTS USING A 3 PERCENT DISCOUNT RATE

[Million 2022$] 

Plant State Class Annualized costs 

(millions 2022$) 

Camden County Municipal Utilities Authority ........................................................................ NJ .................. A′ .................... $16.2 

City of Wilmington ................................................................................................................. DE .................. A′ .................... 23.9 

Delaware County Regional Water Pollution Control Authority ............................................. DE .................. A′ .................... 9.1 

Gloucester County Utilities Authority .................................................................................... NJ .................. A′ .................... 4.9 

PWD Northeast Water Pollution Control Plant ..................................................................... PA .................. A′ .................... 26.2 

PWD Southeast Water Pollution Control Plant ..................................................................... PA .................. A′ .................... 14.1 

PWD Southwest Water Pollution Control Plant .................................................................... PA .................. A′ .................... 37.6 

Hamilton Township ................................................................................................................ NJ .................. A .................... 3.3 

Lower Bucks County Joint Municipal Authority .................................................................... PA .................. A .................... 1.9 

Total ............................................................................................................................... ........................ ........................ 137.1 

D. Potential Benefits 

Water quality improvements can have 

a wide range of effects on water 

resources and the environmental goods 

and services that they provide, 

including services valued by people 

(e.g., recreation, commercial fishing, 

public and private property ownership, 

existence services such as aquatic life, 

wildlife, and habitat designated uses). 

Some environmental goods and services 

(e.g., commercially caught fish) are 

traded in markets, and thus their value 

can be directly observed. Other 

environmental goods and services (e.g., 

recreation and support of aquatic life) 

cannot be bought or sold directly and 

thus do not have observable market 

values. This second type of 

environmental goods and services are 

classified as ‘‘non-market.’’ The 

estimated changes in the non-market 

values of the water resources affected by 

the EPA’s proposed WQS (hereafter, 

‘‘non-market benefits’’) are additive to 

market values (e.g., avoided costs of 

producing various market goods and 

services). 

To value non-market benefits, the 

EPA used a benefit transfer approach 

based on a meta-analysis of surface 

water valuation studies to evaluate the 

use and nonuse benefits of improved 

surface water quality resulting from 

achievement of the EPA’s proposed 

WQS in the 2019 restored scenario.86

The benefit transfer approach involves 

three main steps: 

1. Estimating water quality 

improvements associated with 

attainment of the EPA’s proposed WQS 

relative to the baseline; 

2. Translating these improvements 

into a water quality index (WQI) that 

can be linked to ecosystem services and 

uses that are valued by society. The 

WQI used for this analysis includes six 

parameters: dissolved oxygen, biological 

oxygen demand (BOD), fecal coliform 

(FC), total nitrogen (TN), total 

phosphorus (TP), and total suspended 

solids (TSS); and 

3. Estimating the dollar value of the 

estimated water quality improvements 

based on estimates of the public’s 

willingness-to-pay (WTP) derived from 

a meta-analysis of surface water 

valuation studies. 

To estimate changes in ecosystem 

services provided in the specified zones 

of the Delaware River following 

attainment of the proposed WQS, the 

EPA obtained water quality modeling 

data from DRBC, including dissolved 

oxygen, TN, and TP levels for various 

effluent treatment scenarios. The EPA 

used DRBC’s modeled output of 

dissolved oxygen levels in the specified 

zones following implementation of 

effluent controls (described in the cost 

section) and based on 2019 conditions 

(as described in the policy scenario 


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87Adjustments are detailed in section 4.2 of the 

associated document, Economic Analysis for the 

Proposed Rule: Water Quality Standards to Protect 

Aquatic Life in the Delaware River. 

88The EPA’s 100-mile radius assumption follows 

Viscusi et al. (2008), which states: ‘The survey 

defined relevant water quality as residing in a 

region that is ‘‘a 2-hour drive or so of your home, 

in other words, within 100 miles.’’ About 80% of 

all recreational uses of bodies of water are within 

such a radius of users’ homes. This 80% figure was 

based on data generated by EPA from the 1996 

National Survey on Recreation and the 

Environment. Data indicates that 77.9% of boating 

visits, 78.1% of fishing visits, and 76.9% of 

swimming recreational visits are within a 100-mile 

radius of a given waterbody. (Citation: Viscusi, W. 

K., Huber, J., & Bell, J. (2008). The economic value 

of water quality. Environmental and resource 

economics, 41(2), 169–187.) 

section). The EPA used the 2019 

restored scenario as the basis for 

representing conditions following the 

implementation of the proposed WQS, 

while making minor adjustments as 

needed 87 to ensure that predicted 

oxygen levels meet the EPA’s proposed 

WQS. This analysis provides insight 

into the water quality improvements 

and benefits that are likely to result 

from implementation of the proposed 

WQS. For the remaining parameters 

included in the WQI (i.e., BOD, FC, and 

TSS), the EPA relied on measured data 

at various locations within the specified 

zones. 

The effluent treatment measures 

implemented in response to the 

proposed WQS would directly affect the 

amount of ammonia nitrogen discharged 

to the specified zones of the Delaware 

River and therefore also reduce BOD. 

However, DRBC’s model does not 

account for the changes in BOD. The 

EPA approximated BOD concentrations 

following effluent treatment by 

assuming that baseline BOD 

concentrations are reduced by the same 

percentage change that dissolved 

oxygen improves within each zone (i.e., 

Zone 3, 4, and Upper 5) of the model. 

The EPA kept levels for the remaining 

parameters (TN, TP, TSS, and FC) 

unchanged from baseline conditions. 

Table 11 of this preamble summarizes 

the percent change in dissolved oxygen 

and BOD by zone between the baseline 

and the 2019 restored scenario. 

TABLE 11—DISSOLVED OXYGEN AND

BIOLOGICAL OXYGEN DEMAND

CHANGES BETWEEN THE BASELINE

AND 2019 RESTORED SCENARIOS

Zone 

Percent 

change from 

baseline a

3 ............................................ 10.8 

4 ............................................ 23.8 

Upper-5 ................................. 8.8 

aThe percent change for dissolved oxygen 

and biological oxygen demand are the same, 

but in opposite directions, i.e., the percent decrease in biological oxygen demand concentration is the same as the percent increase 

in dissolved oxygen concentration. 

To quantify benefits of water quality 

improvements, as is consistent with past 

practice, the EPA analyzed the values 

held by households residing within 100 

miles of the specified zones of the 

Delaware River for water quality 

improvements associated with the 

EPA’s proposed WQS.88 Households 

may consider waters unaffected by the 

EPA’s proposed WQS to be substitute 

waters for those affected, and this can 

influence what households would be 

willing to pay for improvements 

associated with the proposed WQS. The 

EPA deems waters unaffected by the 

proposed WQS within the 100-mile 

buffer around each Census block group 

as viable substitutes. 

The EPA estimated the economic 

value of water quality changes using 

results of a meta-analysis of 189 

estimates of total WTP (including both 

use and nonuse values) for water quality 

improvements, provided by 59 original 

studies conducted between 1981 and 

2017. The estimated econometric model 

allows calculation of total WTP for 

changes in a variety of environmental 

services affected by water quality and 

valued by people, including changes in 

recreational fishing opportunities, other 

water-based recreation, and existence 

services such as aquatic life, wildlife, 

and habitat designated uses. The model 

also allows the EPA to adjust WTP 

values based on the core geospatial 

factors predicted by theory to influence 

WTP, including: scale (the size of 

affected resources or areas), market 

extent (the size of the market area over 

which WTP is estimated), and the 

availability of substitute waters. The 

model also takes into account important 

sociodemographic characteristics, such 

as population and income, which vary 

spatially. 

Table 12 in this preamble presents 

estimated household and total 

annualized WTP value for water quality 

improvements following attainment of 

the EPA’s proposed WQS, based on a 3 

percent discount rate. The total 

annualized value of water quality 

improvements from attainment of the 

proposed WQS is $112.8 million. 

TABLE 12—ESTIMATED HOUSEHOLD

AND TOTAL ANNUALIZED WILLINGNESS-TO-PAY (WTP) FOR WATER

QUALITY IMPROVEMENTS UNDER THE

EPA’S PROPOSED WATER QUALITY

STANDARDS, USING A 3 PERCENT

DISCOUNT RATE

Average 

number of 

affected 

households 

(millions) 

Average 

annual WTP 

per household 

(2022$) 

Total 

annualized 

WTP 

(millions 

2022$, 3% 

discount rate) 

14.96 ......... $8.18 $112.8 

E. Conclusion 

The United States Office of 

Management and Budget requires that 

for ‘‘significant regulatory actions’’ (as 

defined in Executive Order 12866 and 

as amended and reaffirmed by Executive 

Order 14094), that the EPA conduct an 

economic analysis. While this proposed 

rulemaking was not deemed significant, 

the EPA nonetheless conducted an 

economic analysis to evaluate the 

potential costs and benefits associated 

with the WQS in the EPA’s proposed 

rule. For this proposed rulemaking, the 

EPA determined that the potential 

benefits justify the potential costs. The 

EPA estimates that the implementation 

of additional effluent treatment controls 

at certain WWTPs could lead to $137.1 

million in annualized costs over 30 

years (2022$, 3% discount rate). The 

EPA quantified estimated non-market 

benefits through average annual 

household WTP for water quality 

improvements. Annualized non-market 

benefits total $112.8 million per year 

over 30 years (2022$, 3% discount rate). 

The EPA’s monetary estimation of 

benefits does not account for benefits 

related to protections for a critically 

endangered species (Atlantic Sturgeon), 

increased housing values, or increased 

commercial fishing, among other 

benefits. Therefore, the EPA’s 

estimation of non-market benefits is 

likely an underestimate of total benefits 

and thus total benefits could potentially 

equal or exceed estimated total costs. 

X. Statutory and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 14094: Modernizing Regulatory 

Review 

This action is not a significant 

regulatory action as defined in 

Executive Order 12866, as amended by 

Executive Order 14094, and was 

therefore not subject to a requirement 

for Executive Order 12866 review. 


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B. Paperwork Reduction Act (PRA) 

This action does not impose any new 

information collection burden under the 

PRA. OMB has previously approved the 

information collection activities 

contained in the existing regulations 

and has assigned OMB control number 

2040–0049. While actions to implement 

these WQS, if finalized, could entail 

additional paperwork burden, this 

action does not directly contain any 

information collection, reporting, or 

record-keeping requirements. 

C. Regulatory Flexibility Act (RFA) 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities 

under the RFA. This action will not 

impose any requirements on small 

entities. Small entities, such as small 

businesses or small governmental 

jurisdictions, are not directly regulated 

by this rulemaking. 

EPA-promulgated WQS are 

implemented through various water 

quality control programs including the 

NPDES program, which limits 

discharges to navigable waters, except 

in compliance with a NPDES permit. 

CWA section 301(b)(1)(C) and the EPA’s 

implementing regulations at 40 CFR 

122.44(d)(1) and 122.44(d)(1)(A) provide 

that all NPDES permits must include 

any limits on discharges that are 

necessary to meet applicable WQS. 

Thus, under the CWA, the EPA’s 

promulgation of WQS establishes 

standards that states implement through 

the NPDES permit process. While states 

have discretion in developing discharge 

limits, those limits ‘‘must control all 

pollutants or pollutant parameters 

(either conventional, nonconventional, 

or toxic pollutants) which the Director 

determines are or may be discharged at 

a level that will cause, have the 

reasonable potential to cause, or 

contribute to an excursion above any 

[s]tate water quality standard, including 

[s]tate narrative criteria for water 

quality’’ (40 CFR 122.44(d)(1)(i)). 

As a result of this action, if finalized, 

the states of Delaware, New Jersey, and 

Pennsylvania will need to ensure that 

permits they issue include any 

limitations on discharges necessary to 

comply with the WQS established in the 

final rule. In doing so, each state will 

have several choices associated with 

permit writing. While each state’s 

implementation of the rule may 

ultimately result in new or revised 

permit conditions for some dischargers, 

including small entities, the EPA’s 

action, by itself, does not impose any of 

these requirements on small entities; in 

other words, these requirements are not 

self-implementing. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain any 

unfunded mandate as described in 

UMRA, 2 U.S.C. 1531–1538, and does 

not significantly or uniquely affect small 

governments. The action imposes no 

enforceable duty on any state, local, or 

Tribal governments or the private sector. 

E. Executive Order 13132: Federalism 

The EPA has concluded that this 

action does not have federalism 

implications. It will not have substantial 

direct effects on the states, on the 

relationship between the national 

government and the states, or on the 

distribution of power and 

responsibilities among the various 

levels of government. This rulemaking 

would not alter Delaware’s, New 

Jersey’s, or Pennsylvania’s considerable 

discretion in implementing these WQS, 

nor would it preclude any of those 

states from adopting revised WQS and 

submitting them to the EPA for review 

and approval either before or after 

promulgation of the final rule. If the 

states submit and the EPA approves 

revised WQS consistent with the CWA, 

then the EPA would no longer be 

required to promulgate Federal WQS. 

Consistent with the EPA’s policy to 

promote communications between the 

EPA and state and local governments, 

the EPA met with the states of Delaware, 

New Jersey, and Pennsylvania and 

DRBC in the process of developing this 

rulemaking to enable them to have 

meaningful input into its development. 

During these discussions, the EPA 

explained the scientific basis for the 

dissolved oxygen criteria to protect 

aquatic life propagation in the specified 

zones of the Delaware River and the 

overall timing of the Federal rulemaking 

effort. The EPA took these discussions 

with the states into account during the 

drafting of this rulemaking. The EPA 

specifically solicits comments on this 

proposed action from state and local 

officials. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

This action does not have Tribal 

implications as specified in Executive 

Order 13175. This rulemaking will not 

affect federally recognized Indian tribes 

in Delaware, New Jersey, or 

Pennsylvania because the WQS would 

not apply to waters in Indian lands nor 

affect Tribal interests. Thus, Executive 

Order 13175 does not apply to this 

action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

The EPA interprets Executive Order 

13045 as applying only to those 

regulatory actions considered significant 

under section 3(f)(1) of Executive Order 

12866 and that concern environmental 

health or safety risks that the EPA has 

reason to believe may 

disproportionately affect children, per 

the definition of ‘‘covered regulatory 

action’’ in section 2–202 of the 

Executive order. Therefore, this action is 

not subject to Executive Order 13045 

because it does not concern an 

environmental health risk or safety risk. 

Since this action does not concern 

human health, the EPA’s Policy on 

Children’s Health also does not apply. 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not a ‘‘significant 

energy action’’ because it is not likely to 

have a significant adverse effect on the 

supply, distribution, or use of energy. 

This action proposes to establish 

Federal CWA aquatic life water quality 

criteria for specified zones of the 

Delaware River under the jurisdiction of 

the states of Delaware, New Jersey, and 

Pennsylvania. 

I. National Technology Transfer and 

Advancement Act (NTTAA) 

This rulemaking does not involve 

technical standards. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations and Executive 

Order 14096: Revitalizing Our Nation’s 

Commitment to Environmental Justice 

for All 

The information supporting this 

Executive order review is summarized 

below and detailed in the associated 

document, Environmental Justice 

Analysis for the Proposed Rule: Water 

Quality Standards to Protect Aquatic 

Life in the Delaware River, which is 

available in the docket for this proposed 

rule. 

The EPA believes that the human 

health or environmental conditions that 

exist prior to this proposed action result 

in or have the potential to result in 

disproportionate and adverse human 

health or environmental effects on 

communities with environmental justice 

(EJ) concerns. For this EJ analysis, the 

EPA evaluated socioeconomic 

characteristics of communities living 

near the relevant zones of the Delaware 

River compared to communities living 

near other zones of the mainstem 


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89For this analysis, the EPA defines ‘‘urban’’ and 

‘‘rural’’ using the Census Urban Areas designation. 

More information about the Census classifications 

is available at https://www.census.gov/programssurveys/geography/guidance/geo-areas/urbanrural.html. 

90The EPA also considered populations who 

identify as American Indian and Alaskan Native, 

Native Hawaiian and Other Pacific Islander, and 

Some Other Race; however, in the Delaware River 

watershed, these populations represent a very small 

fraction (often less than 1%) of the community 

composition. Therefore, these populations are not 

analyzed further in this EJ analysis. 

91 In the 2016 Technical Guidance for Assessing 

Environmental Justice in Regulatory Analysis, the 

EPA defined vulnerability as the ‘‘physical, 

chemical, biological, social, and cultural factors that 

result in certain communities and population 

groups being more susceptible or more exposed to 

environmental toxins, or having compromised 

ability to cope with and/or recover from such 

exposure.’’ For this EJ analysis, the EPA focused on 

social vulnerability based on the metrics presented 

in table 3 of the associated environmental justice 

analysis, which broadly cover categories of race, 

ethnicity, linguistic isolation, income, poverty, and 

education. These metrics provide insight into 

factors that may affect the ability of communities 

near the Delaware River to respond to 

environmental hazards or cope with reduced 

ecosystem services that may result from inadequate 

water quality. Although these socioeconomic 

metrics are relevant to communities living near the 

Delaware River, they are not intended to be an 

exhaustive list of all factors affecting community 

vulnerability. (Source: United States Environmental 

Protection Agency. (2016). Technical Guidance for 

Assessing Environmental Justice in Regulatory 

Analysis. https://www.epa.gov/sites/default/files/ 

2016-06/documents/ejtg_5_6_16_v5.1.pdf.) 

92The EPA assumes that those living in Census 

block groups that are within the five-mile buffer, 

and therefore closest to the specified zones of the 

Delaware River, are most likely to be directly 

affected by the proposed rule. However, this 

assumption could underestimate directly affected 

communities and impact the results of the 

proximity analysis. Accordingly, the EPA 

conducted a sensitivity analysis using a ten-mile 

buffer and determined that community composition 

was not particularly sensitive to the buffer distance 

applied when comparing the results of the five-mile 

and ten-mile buffer. 

93There are no rural areas within five miles of the 

specified zones in Delaware or Pennsylvania. 94 Delaware River Basin Commission (2022a). 

Delaware River. The relevant zones of 

the Delaware River border highly 

urbanized areas, including cities such as 

Philadelphia and Wilmington. 

Accordingly, the EPA’s analysis 

accounts for the distinction between 

urban and rural communities.89

The EPA obtained data from the 

United States Census Bureau’s 

American Community Survey (ACS) 5- 

year estimates for the years 2017–2021 

at the Census block group level to 

construct a set of eight metrics for use 

in this analysis: (1) Black or African 

American, (2) Asian, (3) Two or More 

Races, (4) Hispanic or Latino, (5) 

Limited English Speaking Household, 

(6) Median Household Income, (7) 

Below 200% of the Poverty Level, (8) 

Education Less than a High School 

Diploma or Equivalent.90 Analysis of 

these eight socioeconomic metrics 

provides insight into the spatial 

distribution and prevalence of certain 

indicators of social vulnerability for 

communities near the Delaware River.91

The EPA extended a five-mile buffer 

from the specified zones to capture 

communities living in close proximity 

to waters affected by the EPA’s 

proposed rule, if finalized.92 Similarly, 

the EPA extended a five-mile buffer 

from other zones of the Delaware River 

to form a comparison group. Given the 

large number of block groups located 

near the mainstem Delaware River, 

communities are analyzed in groups, as 

follows: 

• Delaware Urban Areas: Census 

block groups in urban areas within five 

miles of the specified zones in 

Delaware. 

• New Jersey Urban Areas: Census 

block groups in urban areas within five 

miles of the specified zones in New 

Jersey. 

• Pennsylvania Urban Areas: Census 

block groups in urban areas within five 

miles of the specified zones in 

Pennsylvania. 

• Urban Comparison Group: Census 

block groups in urban areas within five 

miles of the remainder of the mainstem 

Delaware River (i.e., excluding block 

groups within five miles of the specified 

zones). 

• Specified Zones Rural Areas: 

Census block groups in rural areas 

within five miles of the specified zones 

in New Jersey.93

• Rural Comparison Group: Census 

block groups in rural areas within five 

miles of the remainder of the mainstem 

Delaware River (i.e., excluding block 

groups within five miles of the specified 

zones). 

The EPA aggregated data across 

multiple block groups using aerial 

apportionment and a populationweighted mean approach to ensure that 

block groups with larger or smaller 

populations were accounted for 

proportionally to their size. This 

calculation relies on an assumption that 

households are evenly distributed 

within each block group. For Median 

Household Income, the EPA aggregated 

data across multiple block groups using 

a linear interpolation calculation. 

The results of the urban and rural 

proximity analyses differed 

significantly. Urban communities in 

Pennsylvania near the specified zones 

surpassed the comparison group average 

(or were less than the comparison group 

for Median Household Income) for all 

eight socioeconomic metrics. Notably, 

urban communities in Pennsylvania 

near the specified zones are over 1.7 

times more likely to identify as Black or 

African American, 1.7 times more likely 

to live below twice the poverty level, 

and have $23,000 lower median 

household income when compared to 

urban communities near the remainder 

of the mainstem river. Urban 

communities within five miles of the 

specified zones in all three states had 

lower income and higher poverty rates 

than the comparison group. Urban 

communities in Delaware near the 

specified zones also had a higher 

percentage of the population identify as 

Black or African American than the 

comparison group, while urban 

communities in New Jersey had a higher 

percentage of the population that 

identifies as Hispanic or Latino and a 

greater percentage with education less 

than a high school degree than the 

comparison group. Therefore, urban 

communities near the specified zones— 

especially in Pennsylvania—exhibited 

differences in socioeconomic 

community characteristics compared to 

other urban communities near the 

Delaware River. 

On the other hand, rural communities 

near the specified zones did not greatly 

differ from rural communities near other 

parts of the mainstem river. While rural 

communities near the specified zones 

did exceed the comparison group 

average for four metrics (Black or 

African American, Asian, Two or More 

Races, and Limited English Speaking 

Household), the differences were always 

less than three percentage points. 

Therefore, the EPA could not conclude 

that rural communities near the 

specified zones were any more or less 

socially vulnerable compared to other 

rural communities near the mainstem 

Delaware River. 

While neither the urban nor the rural 

proximity analyses directly indicate 

which communities may be 

experiencing potential EJ concerns, they 

provide insight into community 

composition surrounding an 

environmental resource. In general, the 

Delaware River has had two contrasting 

areas of water quality for decades. In the 

relevant zones, water quality for aquatic 

life has been significantly worse than in 

the other zones of the river.94 Urban 

areas near these zones, especially in 

Pennsylvania, contain communities that 

are likely more socially vulnerable than 

urban communities that live near other 

zones of the Delaware River, which have 

better water quality. This trend in water 

quality and dissolved oxygen across the 

watershed, coupled with the 

corresponding differences in 

socioeconomic community composition, 

reveals a potential inequitable 


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95 In this analysis, the EPA is not implying 

causality between poor water quality and 

socioeconomic factors. 

96Residents in PWD’s service area pay a single 

bill that covers both water and wastewater charges; 

for this analysis, the EPA uses the term ‘‘water bill’’ 

to refer to the single bill covering water and 

wastewater charges. 

97The EPA also analyzed a conservative scenario 

in which 100% of costs are passed on to residential 

households. Results of this scenario are available in 

the associated document, Environmental Justice 

Analysis for the Proposed Rule: Water Quality 

Standards to Protect Aquatic Life in the Delaware 

River. 

98 Delaware River Basin Commission. (2022c). 

Social and Economic Factors Affecting the 

Attainment of Aquatic Life Uses in the Delaware 

River Estuary. September 2022 Draft. https:// 

www.nj.gov/drbc/library/documents/

AnalysisAttainability/SocialandEconomicFactors_

DRAFTsept2022.pdf. 

99As of September 1, 2023, the monthly water bill 

for a typical residential consumer in Philadelphia 

is $74.81, which equates to $897.72 annually. 

Source: Philadelphia Water Department. Rate 

Changes Effective September 2023. Web page, 

accessed September 26, 2023. https:// 

water.phila.gov/drops/new-rate-informationeffective-september-2023/. 

100United States Environmental Protection 

Agency. (2023). Clean Water Act Financial 

Capability Assessment Guidance. Document ID: 

800b21001. February 2023. https://www.epa.gov/ 

system/files/documents/2023-01/cwa-financialcapability-assessment-guidance.pdf. 

101City of Philadelphia. (2023). Annual Report to 

the Mayor on the Tiered Assistance Program (TAP). 

Department of Revenue. March 31, 2023. https:// 

www.phila.gov/media/20230526113411/TieredAssistance-Program-TAP-2022-annual-report.pdf. 

102The EPA does not have the necessary data to 

calculate a per household surcharge that could 

increase water bills for higher-income customers, 

nor did the EPA include other assistance programs 

in this calculation. 

103City of Philadelphia. (2017). Philadelphia 

Launches New, Income-Based, Tiered Assistance 

Program. Press Release. Office of the Mayor. June 

20, 2017. https://www.phila.gov/press-releases/ 

mayor/philadelphia-launches-new-income-basedtiered-assistance-program/. 

104City of Philadelphia. (2023). Annual Report to 

the Mayor on the Tiered Assistance Program (TAP). 

Department of Revenue. March 31, 2023. https:// 

www.phila.gov/media/20230526113411/TieredAssistance-Program-TAP-2022-annual-report.pdf. 

105 Id. 

106 Id. 

distribution of an environmental 

resource and access to clean surface 

waters within a single watershed.95

The EPA believes that this action 

would be likely to reduce existing 

disproportionate and adverse effects on 

communities with EJ concerns. 

Specifically, the EPA identified an 

inequitable distribution of an 

environmental resource where 

communities with environmental justice 

concerns have inequitable access to 

clean surface waters that support CWA 

section 101(a)(2) goals for aquatic life. 

The EPA’s proposed rule, if finalized 

and implemented, could help to lessen 

this inequitable distribution of an 

environmental resource by ensuring that 

WQS to protect aquatic life in the 

specified zones of the Delaware River 

meet the objectives of the CWA. 

In addition to the proximity analysis, 

the EPA evaluated the potential 

distribution of costs associated with the 

proposed rule under the 

implementation (policy) scenario 

described in section IX of this preamble 

and further detailed in the EPA’s 

associated document, Economic 

Analysis for the Proposed Rule: Water 

Quality Standards to Protect Aquatic 

Life in the Delaware River. For this 

analysis, the EPA selected Philadelphia 

as a case study based on the results of 

the proximity analysis and the large 

share of total estimated costs potentially 

incurred by the Philadelphia Water 

Department (PWD) compared to other 

WWTPs. 

The EPA used two methods to assess 

the potential financial impact to 

Philadelphia households resulting from 

costs associated with the proposed rule. 

First, the EPA calculated household 

burden by quantifying the potential 

increase to consumer water and 

wastewater bills and calculating the 

percentage of median household income 

spent on water bills with and without 

costs from additional wastewater 

treatment plant controls. Second, the 

EPA examined existing water rate 

structures in Philadelphia and customer 

assistance programs to identify possible 

ways in which the affected 

municipalities could adjust rates to 

lessen the financial burden on lowincome households. 

To determine household burden, the 

EPA analyzed how annual water and 

wastewater bills might change if costs 

associated with additional wastewater 

treatment plant controls at PWD 

facilities are passed on to households 

through increased water bills.96 The 

EPA analyzed the financial impact to 

households if costs were passed on to 

residential households in proportion to 

the estimated wastewater flow 

attributed to residential households.97

DRBC estimates that approximately 15% 

of the flow to PWD is attributable to 

residential sources while 85% is 

attributable to non-residential sources.98

Therefore, the EPA calculated 

household burden assuming 15% of the 

costs associated with additional 

wastewater treatment plant controls 

would be spread evenly among 

Philadelphia households. Under this 

assumption the additional annual cost 

per household is $18.07, which would 

equate to $1.50 per household per 

month.99 For this analysis, the EPA 

analyzed household burden using the 

Residential Indicator in the EPA’s 2023 

Clean Water Act Financial Capability 

Assessment Guidance 100 and 

determined that while the costs 

associated with the proposed rule are 

not expected to substantially impact 

household burden under this scenario, 

water bills still have the potential to be 

placing a high burden on a third of 

Philadelphia’s households. However, 

the actual financial burden faced by 

households depends on many factors, 

including customer assistance programs. 

In July 2017, Philadelphia became the 

first to implement an income-based 

alternative water rate structure through 

creation of the Tiered Assistance 

Program (TAP). This program is 

structured based on household income 

relative to the Federal poverty level 

such that monthly bills are capped at 

2%, 2.5%, 3%, and 4% of monthly 

income for consumers whose income is 

0–50%, >50–100%, >100–150%, and 

>150% of the Federal poverty level, 

respectively.101 TAP discounts are offset 

by a surcharge added to the water bill 

of non-TAP customers. 

For illustrative purposes, the EPA 

analyzed how the TAP rate structure 

might apply to eligible low-income 

consumers with water bills that include 

15% of the costs associated with 

additional PWD wastewater treatment 

plant controls.102 Under the TAP rate 

structure, a three-person household 

with income at or below the poverty 

level would have annual savings of at 

least $294. These savings are 

particularly significant for households 

whose income is half the poverty level 

or below. For example, a household at 

50% of the poverty level would see 

savings of $667. 

However, the effectiveness of the TAP 

rate structure depends in large part on 

participation by eligible households. 

When Philadelphia launched TAP in 

2017, it was estimated that around 

60,000 consumers would be eligible for 

the program.103 However, as of 

December 2022, only 14,712 households 

were actively participating in TAP.104

Equally problematic as low 

participation rates are the high attrition 

rates of TAP participants. In 2022, 9,496 

participants defaulted from TAP due to 

a failure to recertify for the program. Of 

those who defaulted, 75% percent did 

not respond to the city’s request for 

recertification.105 Thus, even though 

Philadelphia enrolled 10,405 

participants in 2022, the high attrition 

rate in the program prevents meaningful 

increases in participation. Philadelphia 

continues outreach efforts to raise 

awareness about TAP; 106 however, this 

large gap in participation indicates that 


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88336 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

107Mack, E.A., Wrase, S., Dahme, J., Crosby, S.M., 

Davis, M., Wright, M., & Muhammad, R. (2020). An 

Experiment in Making Water Affordable: 

Philadelphia’s Tiered Assistance Program (TAP). 

Journal of the American Water Resources 

Association, 56(3), 431–449. https://doi.org/ 

10.1111/1752-1688.12830. 

108 Id. 

the full potential of the program is likely 

not being realized. 

Based on the structure of TAP and the 

current low participation rates, lowincome communities are not necessarily 

protected from high water bills and 

increasing water rates. The way the 

program is designed, non-TAP 

customers subsidize the discounts 

applied to TAP customers. When there 

is high participation, the majority of 

program costs are borne by higher 

income households and participating 

low-income households are protected 

from high water bills and increasing 

water rates (including potential rate 

increases to offset costs associated with 

additional wastewater treatment plant 

technologies). With low-participation 

rates, a higher proportion of low-income 

households are paying the TAP 

surcharge and face higher water rates, 

thus placing an undue burden on lowincome households not participating in 

the program. 

In theory, costs associated with the 

EPA’s proposed rule—if partially or 

fully passed on to residential 

consumers—should not impact the 

lowest income households in 

Philadelphia, assuming high 

participation in TAP. However, the 

current low participation rates in TAP 

indicate that some low-income 

communities are likely burdened by 

high water bills and could potentially 

indirectly bear costs associated with the 

EPA’s proposed rule. Although 

Philadelphia’s TAP is innovative, 

additional work to increase 

participation (through increased 

enrollment and decreased attrition rates) 

can further advance water affordability 

and protect low-income households. 

The example of Philadelphia’s TAP 

illustrates how an income-based rate 

structure can potentially have a 

measurable impact on low-income 

communities. Municipalities potentially 

affected by the EPA’s proposed rule 

might consider holistic ways to advance 

water affordability, which can include 

adoption of alternative water rate 

structures and assistance programs that 

lower water bills for low-income 

households. There are several 

considerations for municipalities if 

choosing to implement a program 

similar to TAP in Philadelphia.107 An 

income-based rate structure, such as 

Philadelphia’s TAP, might be most 

effective for utilities with larger service 

areas and higher income disparities for 

households within the service area. 

When a utility has a large customer 

base, it allows the utility to distribute 

any surcharges (to offset lost revenue) 

among many households.108 In theory, 

this redistribution of costs means that 

the per household surcharge can be 

small and affect higher income 

households who might be less socially 

vulnerable. In addition, the 

effectiveness of an income-based rate 

structure hinges on the participation 

rate of low-income communities. 

Municipalities seeking to implement a 

similar program should consider 

practices to encourage high enrollment 

and high retention rates among qualified 

households. Such practices could 

include automatically enrolling 

households who are concurrently on 

other assistance programs (such as 

SNAP) or ensuring a user-friendly 

process for recertification of eligibility, 

if applicable. By thoughtfully and 

strategically advancing water 

affordability programs, municipalities 

can work towards ensuring that socially 

vulnerable communities are not 

overburdened by expensive water bills. 

List of Subjects in 40 CFR Part 131 

Environmental protection, Indianslands, Intergovernmental relations, 

Reporting and recordkeeping 

requirements, Water pollution control. 

Michael S. Regan, 

Administrator. 

For the reasons set forth in the 

preamble, the EPA proposes to amend 

40 CFR part 131 as follows: 

PART 131—WATER QUALITY 

STANDARDS 

■ 1. The authority citation for part 131 

continues to read as follows: 

Authority: 33 U.S.C. 1251 et seq. 

■ 2. Add § 131.XX to read as follows: 

§ 131.XX Water quality standards to 

protect aquatic life in the Delaware River. 

(a) Scope. (1) The designated use in 

paragraph (b) of this section applies to 

river miles 108.4 to 70.0 of the Delaware 

River for the states of New Jersey and 

Pennsylvania. 

(2) The aquatic life criteria in 

paragraph (c) of this section apply to 

river miles 108.4 to 70.0 of the Delaware 

River for the states of Delaware, New 

Jersey, and Pennsylvania. 

(b) Aquatic life designated use. The 

aquatic life designated use is protection 

and propagation of resident and 

migratory aquatic life. 

(c) Dissolved oxygen criteria. The 

applicable dissolved oxygen criteria are 

shown in table 1 to this paragraph (c). 

TABLE 1 TO PARAGRAPH (c)—DISSOLVED OXYGEN CRITERIA

Season 

Magnitude 

(percent oxygen 

saturation) 

Duration Exceedance frequency 

Spawning and Larval Development (March 1–June 30) ................... 66 Daily Average ........ 10% (12 Days Cumulative). 

Juvenile Development (July 1–October 31) ...................................... 66 Daily Average ........ 10% (12 Days Cumulative). 

74 Daily Average ........ 50% (61 Days Cumulative). 

Overwintering (November 1–February 28/29) ................................... 66 Daily Average ........ 10% (12 Days Cumulative). 

(d) Applicability. (1) The aquatic life 

designated use in paragraph (b) of this 

section applies concurrently with other 

applicable designated uses in New 

Jersey and Pennsylvania for river miles 

108.4 to 70.0 of the Delaware River. 

(2) The dissolved oxygen aquatic life 

water quality criteria in paragraph (c) of 

this section are the applicable dissolved 

oxygen criteria in Delaware, New Jersey, 

and Pennsylvania for river miles 108.4 

to 70.0 of the Delaware River and apply 

concurrently with applicable water 

quality criteria for other parameters. 

(3) The designated use and criteria 

established are subject to Delaware’s, 

New Jersey’s, and Pennsylvania’s 

general rules of applicability in the 

same way and to the same extent as are 

other federally promulgated and stateadopted water quality standards in 

those states. 

[FR Doc. 2023–27758 Filed 12–20–23; 8:45 am] 

BILLING CODE 6560–50–P 


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